Max Speed Attainable with These Fgures

[phillnjack]

hi folks
can somebody on here please state the maximum attainable speed with the figures below
lets say for example with a zero amount of slip (yeah i know) and lets say the boat is the best possible
for speed and drag etc.

revs 5500.
gear ratio..2.09 to 1
propeller 13 inches of pitch
diameter 10 inches.


this is not a joke its a serious question


phill

[phillnjack]

wow im shocked that nobody reading these cannot answer a simple question like this.

come on prop guru's...put down your answers...

and dont forget its miles per hour not kilometers per hour or knotts. mph is what i want.
it can then help settle a dispute.

[capnzee]

wow im shocked that nobody reading these cannot answer a simple question like this.

come on prop guru's...put down your answers...

and dont forget its miles per hour not kilometers per hour or knotts. mph is what i want.
it can then help settle a dispute.
@my guess is about 34 mph, @ 100% not much pitch and no rrrrr,s @2.9:1 Lucky to get 30mph on a boat Rod

[ima75man]

o.k. i like trick question. 29.8 mph at 8 % slip.. u might have faster water than we got over here.. or 32.1 at .01 % slip..

[phillnjack]

These are exactly the answer i was expecting .

its just a guy on this very forum with these exact figures says his boat is doing 39. ??mph
i said its impossible with that ratio,that revs and that prop.

others have chimed in and also say 40 is easy with that set up !!!!!!!!!
i think a touch of the niagra falls would be needed ha ha

but im glad that someone else sees it as around the 30mph mark and not me going mad

thansk guys


phill

[ima75man]

a lesson i learned early in life,never bet against the man making the bet.he knows something u don't.

[phillnjack]

ima75man
what would you call realy good slip figures for a race boat ?
and any idea what the average speedboat slip would be ?

[ima75man]

on a good race boat just a quess 6 to 10 % maybe 8 %.on a speed boat don't know to many varible to consider. just one person opinion

[zul8tr]

hi folks
can somebody on here please state the maximum attainable speed with the figures below
lets say for example with a zero amount of slip (yeah i know) and lets say the boat is the best possible
for speed and drag etc.

revs 5500.
gear ratio..2.09 to 1
propeller 13 inches of pitch
diameter 10 inches.


this is not a joke its a serious question


phill

Max speed zero slip = pitch x engine rpm / (1056 x gear ratio) = 13 x 5500/ (1056 x 2.09) = 32.5 mph
If slip was 10% speed = 32.5 (.90) = 29.3mph.

For other data including slip use this

http://continuouswave.com/cgi-bin/propcalc.pl

[phillnjack]

these were the same speeds i got when i calculated it, and i also used the continuous wave gizmo as well to verify.
its juts that on another part of this forum someone said they have these very figures and the boat goes to 40mph on his gps !!!!!
i said its impossible with these figures and people have jumped on me saying its easy done and ofcourse its possible.

now being the stated engine and props figures etc the only thing i could see to make it possible was it being
measured in kilometers per hour and not miles per hour by the guys gps.
but he claimes his gps is 100% accurate etc and definitely miles per hour !!!!!!.
now a few other people chimed in and said i was totaly wrong, and with these figures 40mph is not uncommon,
and mathmatics is nothing compared to a gps reading ha ha ha

to my mind, everything speed related has to be a mathmatical piece to even get the speed, and a turning propellor at a given pitch and revs can only achive a certain maximum speed.

i know im from england and many things between our language can easily be mis-interpreted, but im glad that the guys
who do know their stuff agree that its only a possible 32.5 at best with these figures.

the boat is on this site and from the usa by the way,not in england, we have slow water.
thanks for all the input on this one,
youve all cheered me up and helped me re-gain a little bit of sanity


phill

[russhill]

With 100% efficiency, speed would be 32.396 mph. You can compote your own efficiency by comparing to actual speed.

[zul8tr]

First off the formula is based on screw propellor theory that is based on a completly submerged propellor and with out cavitation or ventilation. The high speed boats run water piercing props that have a good portion of the blades above water and are ventilated (not cavitating), thus the formula was not based on these conditions. However, I have used the above formula to check against my hydro speeds both with gps and water pickup speedometer and all are within a few mph of each other, I run the prop shaft about 3/4" below the bottom so it is surface piercing. As noted in the calc the key features with boat speed determination are rpm, gear ratio, pitch and slip. RPM s and gear ratio are easy to measure. Pitch is measurable and very dependent on where and how measured, by what equipment, and who does it. The supposed standard is somewhere near the 70% radius at the midpoint of the blade cord. But there are other ways to measure: average across the variable pitch blade at a certain radius, average of many points on the blade at different radius, blade contour mapping, etc. Slip on the other hand is not directly measurable with a tool like pitch. It must be calculated somehow from measured results of speed, rpm and pitch. The usual way is to use the formula above.

When people report pitch most do not know if it is accurate or how is was determined other than the stamp on the blade (if there is one). So that is an important part of the speed and must be accurate. If there are reports of very different speeds than what the above calculation gives than I would suspect a problem with the pitch number they claim that is being used in the calculation.

So with any rig the real answer is speed is what ever you measure with the equipment at hand. Myself absolute speed is not as important as differences in speed with changes made in setup and props. To be the last word on absolute speed just mark off a measured distance and run threw it and record the time with a stop watch and calculate the average speed over that distance like they do at kilo runs or Bonniville.

[HankFrazier]

hi folks
can somebody on here please state the maximum attainable speed with the figures below
lets say for example with a zero amount of slip (yeah i know) and lets say the boat is the best possible
for speed and drag etc.

revs 5500.
gear ratio..2.09 to 1
propeller 13 inches of pitch
diameter 10 inches.


this is not a joke its a serious question


phill
prop calcalations will only get you in the ball park not a exact science after racing boats for 30 years more than one time I have tested 3 props right out of the box. same prop same pitch same boat same water props new from mercury test run back to back with in a short time. and one prop has been as much as 4MPH faster. do the same test the next day with same results.in my opinion its impossible to tell somebody exactly how fast a boat will run by prop cal. if you could their would be no reason to race.just saying.

[russhill]

Obviously, the result can be no more accurate than the input GIGO

[David Mason]

I have raced boats for a great number of years. One thing experience has taught me. Never go by an instruction manual, and never believe a theory. If we all went by the books and theories, where would the world be today ? Think Mr. K listened to the critics when he developed an outboard ?

One huge thing to think about, what works on one persons rig might not work well on another. There are way to many foctors at play to calculate anything accurately. I would say add or subtract ten MPH from those sums. Those formulas get you to a starting point, after that it is up to the individual to tweak and achieve the desired result. In addition, those formuals do not account for certain modifications some do internally. Like I said, way to many things to account for each one. Testing is key.

[HankFrazier]

i have raced boats for a great number of years. One thing experience has taught me. Never go by an instruction manual, and never believe a theory. If we all went by the books and theories, where would the world be today ? Think mr. K listened to the critics when he developed an outboard ?

One huge thing to think about, what works on one persons rig might not work well on another. There are way to many foctors at play to calculate anything accurately. I would say add or subtract ten mph from those sums. Those formulas get you to a starting point, after that it is up to the individual to tweak and achieve the desired result. In addition, those formuals do not account for certain modifications some do internally. Like i said, way to many things to account for each one. Testing is key.
well said.

[MWhite]

I have raced boats for a great number of years. One thing experience has taught me. Never go by an instruction manual, and never believe a theory. If we all went by the books and theories, where would the world be today ? Think Mr. K listened to the critics when he developed an outboard ?

One huge thing to think about, what works on one persons rig might not work well on another. There are way to many foctors at play to calculate anything accurately. I would say add or subtract ten MPH from those sums. Those formulas get you to a starting point, after that it is up to the individual to tweak and achieve the desired result. In addition, those formuals do not account for certain modifications some do internally. Like I said, way to many things to account for each one. Testing is key.

Exactly, well said.

[ima75man]

sounds good to me...the problem some have they cheat themselves,

[omcstratos]

I have raced boats for a great number of years. One thing experience has taught me. Never go by an instruction manual, and never believe a theory. If we all went by the books and theories, where would the world be today ? Think Mr. K listened to the critics when he developed an outboard ?

One huge thing to think about, what works on one persons rig might not work well on another. There are way to many foctors at play to calculate anything accurately. I would say add or subtract ten MPH from those sums. Those formulas get you to a starting point, after that it is up to the individual to tweak and achieve the desired result. In addition, those formuals do not account for certain modifications some do internally. Like I said, way to many things to account for each one. Testing is key.

I'd give this the best answer vote

[phillnjack]

Ahhh yes, i agree with the testing
but theory when given figures can only be right in the maximum possible.
to get to that figure is where the testing comes into play.
all the testing in the world cannot get you past the maximum possible attainable speed. !!!! the testing is trying to get as close as possible to this speed is what its all about.

we all like to think our boats and cars are farster than they are, ive raced car down the drag strip years ago.
and the amount of times i beat cars that were supposed to be sub 9 second cars was unbelievable.
I never got to maximum theory, neither did donald cambell, neither has anyone who has broken the
landspeed record or air speed record.
No boat has ever gone past or even too its maximum mathematical speed, !!! this is due to many factors.
the boat being the main factor in this case, the absolute perfect boat with zero drag/slip has yet to be invented.
there is no boat anywhere in the world that dont have a certain amount of drag.
And there has not yet been a propeller invented that is 100% perfect, they all have a certain amount of slip and drag to them.

but given a set if figures like revolutions per minute, and a gear ratio and a given size propeller, there is a
maximum speed, there is not getting around it with testing and raising the engine, lowering the the engine or filling
the boat up with helium,the max speed is max speed and that is the target, it cannot possibly be passed.

now anyone who thinks there boat is faster than the maximum calculated speed given the figures of rpm's, gear ratio, and prop pitch is a fool who is lying to himself.
and he is not fooling anyone.

at the top i gave figures, the figures are easy to calculate or to use on a formular, the speed reached can never ever possibly be faster....its just a fact.

test as much as you like with a gps, but dont take ya gps as gosple, no world records rely on gps they use a set length
and a timer, its far more accurate than gps.
with gps you are relying on the satelites , gps is great for pin pointing, but even then not 100%.
gps is a signal sent from a device to a set of satelites and then bounced back, this again takes time.

but in this particular case, the gps is way off target by around 20%.... or the figures quoted of pitch,rpm and gear ratio.
the gear ratio is not suspect in this case as its not going to be different.

33mph with a very good tail wind (hurricane strength) COULD be possible on a race boat.

but what a boat that would be



phill

[phillnjack]

ima75man has hit the nail on the head.

they cheat themself.

hank i understand you had a prop 4mph, but at what speed are we talking about ?
in this case the prop just has to be 8 miles per hour different on just a theoretical 32 mph ?
have you gone past theoretical maximum speed EVER and had a boat with no drag or slip at all ?..


omc stratos
do you think its possible to get 10mph more than a maximum possible speed with given factors ?????

[MWhite]

Ahhh yes, i agree with the testing
but theory when given figures can only be right in the maximum possible.
to get to that figure is where the testing comes into play.
all the testing in the world cannot get you past the maximum possible attainable speed. !!!! the testing is trying to get as close as possible to this speed is what its all about.

we all like to think our boats and cars are farster than they are, ive raced car down the drag strip years ago.
and the amount of times i beat cars that were supposed to be sub 9 second cars was unbelievable.
I never got to maximum theory, neither did donald cambell, neither has anyone who has broken the
landspeed record or air speed record.
No boat has ever gone past or even too its maximum mathematical speed, !!! this is due to many factors.
the boat being the main factor in this case, the absolute perfect boat with zero drag/slip has yet to be invented.
there is no boat anywhere in the world that dont have a certain amount of drag.
And there has not yet been a propeller invented that is 100% perfect, they all have a certain amount of slip and drag to them.

but given a set if figures like revolutions per minute, and a gear ratio and a given size propeller, there is a
maximum speed, there is not getting around it with testing and raising the engine, lowering the the engine or filling
the boat up with helium,the max speed is max speed and that is the target, it cannot possibly be passed.

now anyone who thinks there boat is faster than the maximum calculated speed given the figures of rpm's, gear ratio, and prop pitch is a fool who is lying to himself.
and he is not fooling anyone.

at the top i gave figures, the figures are easy to calculate or to use on a formular, the speed reached can never ever possibly be faster....its just a fact.

test as much as you like with a gps, but dont take ya gps as gosple, no world records rely on gps they use a set length
and a timer, its far more accurate than gps.
with gps you are relying on the satelites , gps is great for pin pointing, but even then not 100%.
gps is a signal sent from a device to a set of satelites and then bounced back, this again takes time.

but in this particular case, the gps is way off target by around 20%.... or the figures quoted of pitch,rpm and gear ratio.
the gear ratio is not suspect in this case as its not going to be different.

33mph with a very good tail wind (hurricane strength) COULD be possible on a race boat.

but what a boat that would be



phill

and that my friends is the LESSONS for today, stay tune more to come.

[phillnjack]

do i take it you have more than the max possible speed on your boat mike ?

lets hear your cliam on what it is and the revs etc etc etc.

[HankFrazier]

ima75man has hit the nail on the head.

they cheat themself.

hank i understand you had a prop 4mph, but at what speed are we talking about ?
in this case the prop just has to be 8 miles per hour different on just a theoretical 32 mph ?
have you gone past theoretical maximum speed EVER and had a boat with no drag or slip at all ?..


omc stratos
do you think its possible to get 10mph more than a maximum possible speed with given factors ?????
TO be totally honest I have never used prop cal.i have always done my testing on the water and never thought about max speed cal. I can tell u for sure no two props run exactly alike two major factors in how fast my boat is are how much trim u put in the motor and how much chop is on the water I can easly scrub off 10 mph by not trimming enough the rpm's will be the same but not the speed. the three props that I was talking about were 20 pitch mercury clevers lab finished at mercury the fastest ran 74 the slowest ran 70 all about same rpm. all I am saying it is impossible to tell someone exactly how fast their boat will run on a given day with a calcalater.i would rather race to find out. u were in the infield at the ballpark on my speed.

[Mark75H]

The ban is for harassing members via PM. When one signs up on BRF, one agrees NOT to engage in such behavior.

[champ20B]

hi folks
can somebody on here please state the maximum attainable speed with the figures below
lets say for example with a zero amount of slip (yeah i know) and lets say the boat is the best possible
for speed and drag etc.

revs 5500.
gear ratio..2.09 to 1
propeller 13 inches of pitch
diameter 10 inches.


this is not a joke its a serious question


phill Well, you indicate that this would be a very dynamically designed hull (best for speed/drag etc.) so lets go with an 80% efficiency. 5500/2.09=2631.58 RPM 2631.58RPM x 13 inches = 34210.526 inches/minute 34210.526in/min x 60minutes = 2052631.579inches/hour 2052631 in/hour / 12 inches= 171052.632 ft/hour
Now that we have feet per hour, lets divide it by 5,280 feet,which is a mile.................... 171052.632/5280= (32.4 MPH)
32.4 MPH x (80% efficiency) = ----25.92 MPH-----
Your rig will likely run between (24 and 29 MPH) give or take......... And thats a wild guess!!! LOL!!

[pdt]

champ im with you all the way on this one, seems you have the same conclusion that were made previously.
but others for some reason think this boat with these figures can be running at 40mph !!!!!!!!!!!!
I say its a total impossibility with these figures.
it seems champ that you and me are the only ones who can see there is a maximum speed attainable with any set up.
once you know the maximum revs and the prop size and gear ratio, the maximum possible speed is very easy to see, but no boat will ever reach its
theoretical maximum due to water drag/slip etc.
I don't even think a boat exists that is 95% drag free yet, even the most powerfull drag boats don't allways get the same top speeds time after time after time.
there is not even a race car or aeroplane that can run 100% efficiency.

I think 80 to 85 % is a pretty reasonable target for the average recreational speedboat, and 93% is very good even for a race boat.

could be wrong !!!

[Mark75H]

I believe you are correct

[Nason]

What would be max speed on 16p, 1.83 gears and 7400rpms?

[pdt]

maximum possible speed with those figures would be 61mph, but that would be impossible to reach with a boat on water,
it would be nearer to 56mph with a slip of just 8%
that would be a good figure to attain without spending a fortune on getting the perfect racing hull and being ultra lightweight.

[omcstratos]

I have raced boats for a great number of years. One thing experience has taught me. Never go by an instruction manual, and never believe a theory. If we all went by the books and theories, where would the world be today ? Think Mr. K listened to the critics when he developed an outboard ?

One huge thing to think about, what works on one persons rig might not work well on another. There are way to many foctors at play to calculate anything accurately. I would say add or subtract ten MPH from those sums. Those formulas get you to a starting point, after that it is up to the individual to tweak and achieve the desired result. In addition, those formuals do not account for certain modifications some do internally. Like I said, way to many things to account for each one. Testing is key.

Still agree with this. So many variables to work with. Pitch can also vary from prop to prop, and is not always accurate. Nothing compares to the real testing.

[Nason]

maximum possible speed with those figures would be 61mph, but that would be impossible to reach with a boat on water,
it would be nearer to 56mph with a slip of just 8%
that would be a good figure to attain without spending a fortune on getting the perfect racing hull and being ultra lightweight.

Guess I am doing good 56.9 / 57 mph on 2 different gps and 57.3 was the best

[champ20B]

What would be max speed on 16p, 1.83 gears and 7400rpms?

7400RPM??!!!! Wow!!! You must have one "bad to the bone" outboard running them kind of revs!!!! LOL!!
Anyway, you would theoretically get 61.27 MPH. But at about 80% you'll see 49-50 MPH. Now, at 90% you will see about 55MPH. Estimate, about 47-57 MPH give or take, depends on the weight, or the wind at your back, stayin on track!!

[pdt]

need to post up some video's and pictures of this boat Nason.
im sure loads of people would love to see this in action, sounds like a real ultra high performance race boat to get those speeds.
your slip percentage is fantastically low, great set up.

.

[Nason]

Don't know how to post videos give me a email address and you can post it.

[omcstratos]

I'd like to see that actually. You got a pic of your setup or anything? Send me some pics here or PM.

[Nason]

sent 2 videos to pdt if you like post your email and I will send them to you also

[Nason]

need to post up some video's and pictures of this boat Nason.
im sure loads of people would love to see this in action, sounds like a real ultra high performance race boat to get those speeds.
your slip percentage is fantastically low, great set up.

.

Pdt you saw the videos what are your thoughts?

[pdt]

nice boats
I do like the way it jumps up onto plane very quickly, and not a lot of boat in the water when running full throttle.
obviously set up dead right.

what is it like the rough water ? or have you not got rough stuff out there

[MWhite]

maximum possible speed with those figures would be 61mph, but that would be impossible to reach with a boat on water,
it would be nearer to 56mph with a slip of just 8%
that would be a good figure to attain without spending a fortune on getting the perfect racing hull and being ultra lightweight.

impossible to reach with a boat on water,, I can run this speed all day long in my boat, so its not impossible.

[omcstratos]

sent 2 videos to pdt if you like post your email and I will send them to you also

Would you like them posted?

[Nason]

sure if you want to

[omcstratos]

It's actually on phillnjack's youtube channel
http://www.youtube.com/watch?v=plO0s99PE94

[omcstratos]

I like the pad bottom boat that planes off and does a run

[pdt]

nice boats

[pdt]

Those boats look very very lightweight, and look like speedboats without the tops on them.
good bit of video showing them running good and almost no boat hull in the water.
need lots more vids like this showing what the boats run like.

[MWhite]

Still agree with this. So many variables to work with. Pitch can also vary from prop to prop, and is not always accurate. Nothing compares to the real testing.

david mason is right and so is omcstratos on this,, theres to many things to take in account. the ones who disagree with this has never had any experinces playing,setting up boats or racing boats period. like omcstratos and mason said nothing compares to real testing.

[HankFrazier]

JOHN WAYNE once said LIFE IS HARD BUT IT'S REALLY HARD IF YOUR STUPID.

[pdt]

your drifting again and trying so hard to cause a problem .
the testing is trying to get to maximum possible, or it would be of no use, you cannot go past maximum possible, your trying (very trying) to get as close as posible

with a given set of genuine figures for the rpm, a set of genuine figures for the gear ratio and a set of genuine figures for pitch there has to be a maximum permissible velocity attainable.

6000 rpm with 2-1 gear set and 24 inch pitch prop . maximum possible speed = 68.181818
with this simple sum there is no variables, only constants.

[omcstratos]

your drifting again and trying so hard to cause a problem .
the testing is trying to get to maximum possible, or it would be of no use, you cannot go past maximum possible, your trying (very trying) to get as close as posible

with a given set of genuine figures for the rpm, a set of genuine figures for the gear ratio and a set of genuine figures for pitch there has to be a maximum permissible velocity attainable.

6000 rpm with 2-1 gear set and 24 inch pitch prop . maximum possible speed = 68.181818
with this simple sum there is no variables, only constants.

Maximum speed attainable given that the pitch stamped on the prop is indeed TRUE and not under

[fs5]

or over pitched from whats stamped on it,sometimes tacko's are out to.even the old gps can tell a porky sometimes...

[pdt]

That's the thing with most tall stories of speed on water, the facts that are given are wrong, in many cases impossible speeds are given for the goods they are running.
I know some don't know the difference between knots kms per hour and miles per hour .

[zul8tr]

This is getting long in the tooth. Speed issue resolved.

If you want your rig to be fast just read the mph on the gps or water pickup speedo and report the value as knots and it will going about 15% faster.

[omcstratos]

This speed calculation stuff is beginning to get redundant...

[R Pierson]

Been watching your thread....

Couple of observations. I have found over the last 30 years of doing this that what is stamped on the prop is kind of irrelevant. With these new progressive pitch props, the part of the blade that does the most work at the trim setting and rpm you are evaluating is the most relevant info. Crab angle ( the more you have the less active pitch you have to work with) and trim angle ( tucked under vs trim past parallel Under adds and trim out takes away) effects the pitch as it is attacking the water. Ron Hill showed me 20 years back using lipstick, of all things, that we could find the part of the blade doing the most work. Then you could accurately find the slip numbers based on the pitch that was on that part of the blade. The part of the blade toward the leading edge and near the hub does the most work on initial take off. As rpm increases, centrifical force causes it to move out toward the tips and the faster you go...same result. I found out many years ago that all the calculations are kind of moot. I'd rather have a prop with 30% slip than one with 10% if the 30% one was faster. We also found that the prop swing from about 2-3 o-clock to about 7 o-clock did the most work ( on right hand rotation stuff). Some of this came from guys like Dave Bostic of Hoss props. Dave even showed Mercury that when they take off the rear prop on the ill fated Blackhawk twin prop drive...not much happened. But...putting on a prop with 20% more pitch than the front prop, it started to work. Then they sh&% canned the drive..so much for that.

Also, I never understood why everyone thought slip was a bad thing. Slip is thrust. If an airplane prop had no slip....the plane would fall out of the sky. Dennis Cavanaugh from Merc High perf ( before he passed away) was brilliant on this subject.

So...when we set up any boat at my shop, crab angle of the motor and getting a prop to run without much positive trim is the first priority. That tell us we have a good set up..prop included. If you are running a ton of positive trim or the engine is crabbed a bunch the prop or set up in general are not doing the job.

Hope that gets you guys thinking out of the box a bit..

I've wrecked a ton of props in my day modifying them...but I've also have some wonder-props come from that experimentation.

[pdt]

This is great, I have not laughed this much for ages, please keep it up, its cold and boring on tv, this is fantastic entertainment .

and there was me thinking that nobody here has a sense of humour, then along comes a brilliant comedian,, great stuff.

[pdt]

admin please lock this topic, my ribs are killing me, I cant take much more.

just incase I die laughing merry xmas guys

[Ron Hill]

Randy made the point that he'd rather have a prop with 30% slip, if it went faster than a prop with 10% slip. Looks at these pictures:1. The Prop Scan cost $27,000 and you can make a 4 million measurements on one prop blade, the next prop blade might be different. Propellers that are CNC's are perfect, because it is really very hard to get "PERFECT". Look at this three blade: At the leading edge it is 22 1/12 or such, 24 in the middle, and m26 or 27 on the out pitch. This is an OLD mechanical gauge, and we only use it to measure ONE radius on props. It really is just a "GOOD GUESS", as I measure a new Mercury propeller yesterday, it was supposed to be an 18....It went 16-19 1/2 20 on the three spots I measured it. Mercury calls it an 18. I'd call it an 18.5 at where I measure it. This five blade, is like the one Randy ran at Parker on the 250 Yamaha 4 Stroke. We call it a 15 5/8 X 32. It would go about 94, unless you wanted to "PUCKER" and then 100 was right there. Is it a 32, how fast will it go????As Greg Foster says, "Give me a happy prop" and I'll win the race. "Happy" meaning something that doesn't require a bunch of trim, something that will push the boat on an even keel!

[MWhite]

That's the thing with most tall stories of speed on water, the facts that are given are wrong, in many cases impossible speeds are given for the goods they are running.
I know some don't know the difference between knots kms per hour and miles per hour .

What tall stories u refuring to?? facts are what they are and there not wrong, and the gps don't lie. your calculations and figures are only good on paper, that's it, on the water it a different story and u can throw all that away...If u don't believe it,,,, that's your problem.

[Ron Hill]

My Mark 30-H would turn 7,200 RPM's on a good day. My Mark 55-H would also turn 7,200 on a good day. We were at Modesto Reservoir in Waterford, California for the APBA Stock Nationals. Weather was dry and borderline 90 plus. My first run in my C Runabout was 60 MPH but over the old record. My dad said, "For the second run put your D Hydro wheel on." I did and I broke the C Runabout UIM record at 64.661. It may still be a record. I then, took the same prop off my "C" (30-H) and put it on my D Runabout (55-H). I broke the D Runabout record (I think the speed was 70.456). Both flat bottoms, both 7,200 RPM motors, one a 30 cubic inch, one a 40 cubic inch....One with an A-B-C Quickie, one with a "D" Quickie...One at 425 pounds, one at 550 pounds. The same prop would go 76 MPH on my brother Sid Craft Sid Hydro. The motor only turned 7,200 RPM's....In 1966, I ran this same prop on my Quincy "A" Looper for a Kilo Record of 71 MPH....The Looper was probably turning 8,000 but with has 16:21 gears...How fast will a prop go?????? Check the GPS!!

[MWhite]

My Mark 30-H would turn 7,200 RPM's on a good day. My Mark 55-H would also turn 7,200 on a good day. We were at Modesto Reservoir in Waterford, California for the APBA Stock Nationals. Weather was dry and borderline 90 plus. My first run in my C Runabout was 60 MPH but over the old record. My dad said, "For the second run put your D Hydro wheel on." I did and I broke the C Runabout UIM record at 64.661. It may still be a record. I then, took the same prop off my "C" (30-H) and put it on my D Runabout (55-H). I broke the D Runabout record (I think the speed was 70.456). Both flat bottoms, both 7,200 RPM motors, one a 30 cubic inch, one a 40 cubic inch....One with an A-B-C Quickie, one with a "D" Quickie...One at 425 pounds, one at 550 pounds. The same prop would go 76 MPH on my brother Sid Craft Sid Hydro. The motor only turned 7,200 RPM's....In 1966, I ran this same prop on my Quincy "A" Looper for a Kilo Record of 71 MPH....The Looper was probably turning 8,000 but with has 16:21 gears...How fast will a prop go?????? Check the GPS!!

that was a good prop, I bet u still have it to. The gps don't lie, it may even hurt your feelings too. lol

[Ron Hill]

Over the years, I've dealt with a lot of boaters. Guys with big assed Chevy motors with blowers or nitro burnering flat bottoms have always been the biggest "PAINS". Until the GPS came out many of these "FLAT BOTTOM" guys wanted to turn their engine 7,500 or 8,000 RPM. I'd frequently tell them, why not just take the prop off and turn it what every RPM you want??? Why people started using GPS's I had a guy tell me he'd spent $25,000 trying to gain speed by in creasing horse power. He had gain 200 HP and gained no MPH. My prop, first run out gained him 8 MPH, at 500 RPM less. The GPS has made me a lot of money. Figures don't lie, but liars figure! The GPS is actually pretty simple...You go 80 the GPS says, you go 80....period, end of BS!!1

[champ20B]

Over the years, I've dealt with a lot of boaters. Guys with big assed Chevy motors with blowers or nitro burnering flat bottoms have always been the biggest "PAINS". Until the GPS came out many of these "FLAT BOTTOM" guys wanted to turn their engine 7,500 or 8,000 RPM. I'd frequently tell them, why not just take the prop off and turn it what every RPM you want??? Why people started using GPS's I had a guy tell me he'd spent $25,000 trying to gain speed by in creasing horse power. He had gain 200 HP and gained no MPH. My prop, first run out gained him 8 MPH, at 500 RPM less. The GPS has made me a lot of money. Figures don't lie, but liars figure! The GPS is actually pretty simple...You go 80 the GPS says, you go 80....period, end of BS!!1

That's the only way to do it, GPS then math or math then GPS, however one wants to do it to estimate % slippage. Otherwise, one better have someone on shore with a keen eye and a good stop-watch after measuring distance between bouys!

[fs5]

a "good" gps won't lie ,the ones that come on mobile phones do ....which a lot of guys use now days.i've recorded a top speed of 258kph runnin a little 18p chopper on my slt boat and a lot of other numbers I wish was real...also about 10 years back had the best hand held huming bird in its day and it told me I was doin 64mph at 4000 rpm cruising with a 20p...
the good ones nowdays are real accurate,and they break a lot of hearts.
I like the comment about if a prop ran faster with 30% slip..thats it,if your out in front who cares..a lot of guys try chasing a number.theres nothing better sittin side by side tryin your best to get round him.

[MWhite]

Over the years, I've dealt with a lot of boaters. Guys with big assed Chevy motors with blowers or nitro burnering flat bottoms have always been the biggest "PAINS". Until the GPS came out many of these "FLAT BOTTOM" guys wanted to turn their engine 7,500 or 8,000 RPM. I'd frequently tell them, why not just take the prop off and turn it what every RPM you want??? Why people started using GPS's I had a guy tell me he'd spent $25,000 trying to gain speed by in creasing horse power. He had gain 200 HP and gained no MPH. My prop, first run out gained him 8 MPH, at 500 RPM less. The GPS has made me a lot of money. Figures don't lie, but liars figure! The GPS is actually pretty simple...You go 80 the GPS says, you go 80....period, end of BS!!1

u got that right ron,, end of BS and calculations and figures.

[zul8tr]

Measured distance and stop watch is what I used down one of the SFWMD canals in West Palm Beach with Mark and his Dad Ed Hauptner there sometimes with their tunnels.

Seems we have discussed all the stuff enough and hope it is settled? Besides I am out of popcorn and those little chocolate thingies with the white sprinkles on them!

[pdt]

Ron hill wrote "Figures don't lie, but liars figure!"

well said ron.

Took a long time, but atleast now people agree when its someone else saying it..

own goal :cool:

[Ron Hill]

I stated what I thought to be a fact: 7,200 RPM motor, one 30 cubic inches, one 40 cubic inches. The 40 went faster at the same RPM. Is this true? Is this possible? If so, why?

[HankFrazier]

Over the years, I've dealt with a lot of boaters. Guys with big assed Chevy motors with blowers or nitro burnering flat bottoms have always been the biggest "PAINS". Until the GPS came out many of these "FLAT BOTTOM" guys wanted to turn their engine 7,500 or 8,000 RPM. I'd frequently tell them, why not just take the prop off and turn it what every RPM you want??? Why people started using GPS's I had a guy tell me he'd spent $25,000 trying to gain speed by in creasing horse power. He had gain 200 HP and gained no MPH. My prop, first run out gained him 8 MPH, at 500 RPM less. The GPS has made me a lot of money. Figures don't lie, but liars figure! The GPS is actually pretty simple...You go 80 the GPS says, you go 80....period, end of BS!!1
WELL SAID! I have been running boats since i was 15 years old and I am almost 50 now and have been all over the southern states racing mostly for fun and bragging rights out run a lot of people and have been outrun a few times.AND OUT OF ALL THIS RACING AND FUN I HAD RACING NOT ONE TIME DID WE EVER RACE ON PAPER INSTEAD OF WATER. READING THIS BS IS GETTING OLD.

[MWhite]

Ron hill wrote "Figures don't lie, but liars figure!"

well said ron.

Took a long time, but atleast now people agree when its someone else saying it..

own goal :cool:

your figures and calculations are only good on paper. THATS ITS. and no one agrees with u.

[pdt]

Mike you do agree with me, but of course you just cannot bare to admit I am right.

come on mike lets put it to the test, see who's so wrong shall we.
what is the very maximum revs, gear ratio and prop size you get with your engine at the highest speed you get ? don't tell me the speed, just the ratio, prop, and rpm's.

don't forget I can only tell you its maximum possible, not actual as you will be a bit slower , though probably not by much.!!!!!!!!

you and your friends will probably already know these figures to the very finest detail.

[pdt]

ron said
I stated what I thought to be a fact: 7,200 RPM motor, one 30 cubic inches, one 40 cubic inches. The 40 went faster at the same RPM. Is this true? Is this possible? If so, why?

if on the same boat with same gear ratio and same prop with all other things like weight wind etc it could be a small amount either way, but hardly any difference.
But none of them exceeded the maximum mathematical target did they ron ????????????

there guys out there running thousands of horsepower on mega lightweight drag boats not doing it, its the very reason why records get broken.

[HankFrazier]

yOU CAN TAKE THE DUMBEST GUY IN THE WORLD PUT HIM IN A THREE PIECE SUIT AND SIT HIM AT A TABLE WITH THE SMARTEST MEN IN THE WORLD AND NOBODY WILL KNOW HOW DUMB HE IS AS LONG AS HE KEEPS HIS MOUTH SHUT.

[pdt]

So your saying that most of the people answering this thread wear suits ?

that's not very nice now is it.

[MWhite]

So your saying that most of the people answering this thread wear suits ?

that's not very nice now is it.

I have yet to master the art of teaching a man who refuses to listen. Ignorance is curable, stupidity is forever.

[MWhite]

Mike you do agree with me, but of course you just cannot bare to admit I am right.

come on mike lets put it to the test, see who's so wrong shall we.
what is the very maximum revs, gear ratio and prop size you get with your engine at the highest speed you get ? don't tell me the speed, just the ratio, prop, and rpm's.

don't forget I can only tell you its maximum possible, not actual as you will be a bit slower , though probably not by much.!!!!!!!!

you and your friends will probably already know these figures to the very finest detail.

No i dont, and ron dont agree with u eithier, r u so blind u dont see this. I know what im running and i dont need u to calculate nothin for me, i've forgot more than you'll ever know,, this is all im going to say on this BS, this has got old and i dont have time to argue with dum people like u.

[HankFrazier]

So your saying that most of the people answering this thread wear suits ?

that's not very nice now is it.
I'M ONLY STATING A FACT THE SMART PEOPLE ON THIS THREAD CAN TELL WHAT YOU ARE WEARING BY THAT ENDLESS STREAM OF BULL**** THAT YOU KEEP GOING ON AND ON ABOUT. HAVE YOU EVER BEEN IN A RACE OR RACE BOAT/ if you have prove it post pictures and speeds.Let us see how fast you can make a boat go.

[omcstratos]

I am getting tired of this, now I get PMs about it...


is everyone on this forum taking the p..s or are they really as stupid as they are coming across ?

just do this sum for me, ill break it up to prove a point for once.

forget about wind weight blah blah blah for now.


5,000rpm with 2-1 gear ratio gives us 2500rpm at the prop right ?
we use a 12 inch pitch prop for ease of calculation, so its now 2500 feet per minute due to every turn of the prop is 12 inches. ..ok so far so good.

now we times that by 60 for the minutes of an hour and we get 150,000 feet ok...so far very easy ha ha
now we simply dived that number by 3 to give us yards, ( 3 feet = 1 yard) so we now have 50,000 yards per hour now....still with me, great stuff.

now simply dive the 50,000 yards by 1760 to get miles per hour and we have arrived at ????????? mph..that is maximum,
if a guy tells you his boat does this with these figures then he is a lying retard.

its impossible, this is absolute max speed, not what it will do, this is only possible with a weightless boat with no air drag and no water drag, it would need to be 100% perfection
for the drag both underwater and above, the weight would need to be total zero as well.


it has to be a American v English joke,nobody can be that thick not to understand maximum speed etc.

by the way the speed in the math above will be 28.409 mph


phill


Is this ever going to end???? You can't teach an old dog new tricks and you cant persuade Phill to put pen and paper theory aside.

[champ20B]

I am getting tired of this, now I get PMs about it...




Is this ever going to end???? You can't teach an old dog new tricks and you cant persuade Phill to put pen and paper theory aside.

LOL!!!!!!! If anyone could ever make a prop, or vessel as well for that matter, that will run in water at 100%, they would be BILLIONARES OVERNIGHT!!!!!! Hell, they'd rule the industry from powerskiffs to battleships.
There can be close calls (90+%), but 100% wont ever happen.

[champ20B]

LOL!!!!!!! If anyone could ever make a prop, or vessel as well for that matter, that will run in water at 100%, they would be BILLIONARES OVERNIGHT!!!!!! Hell, they'd rule the industry from powerskiffs to battleships.
There can be close calls (90+%), but 100% wont ever happen.

I don't know what all the hen-house squabble is for in reference to math. MATH DOESN'T LIE AND THE LAW OF PHYSICS DON'T CHANGE FOR NOBODY!!! All the pitch/RPM calculations are for is to determine prop slip.... AFTER TESTING!!!!!!!!!!!!!!!!
THAT IS IT!!!! Beyond that, you either have a good prop or some peice of crap that somebody carved on or cobbled up or a bad set up overall. PERIOD!!!

[Ron Hill]

LOL!!!!!!! If anyone could ever make a prop, or vessel as well for that matter, that will run in water at 100%, they would be BILLIONAIRES OVERNIGHT!!!!!! Hell, they'd rule the industry from powerskiffs to battleships.
There can be close calls (90+%), but 100% wont ever happen.

I had a 15 X 30 on my V-8 Johnson than ran through the kilo at 118 MPH. At that time, we figured it was 110% efficiency. I concluded, that Mercury didn't include the CUP as part of their pitch.

[pdt]

champ you have said it perfectly, thank you very much.

I was losing the will to live,.

im so glad to know there is someone else out there on the forum who truly understands physics.

once again thanks


now let the thread close.

[MWhite]

I don't know what all the hen-house squabble is for in reference to math. MATH DOESN'T LIE AND THE LAW OF PHYSICS DON'T CHANGE FOR NOBODY!!! All the pitch/RPM calculations are for is to determine prop slip.... AFTER TESTING!!!!!!!!!!!!!!!!
THAT IS IT!!!! Beyond that, you either have a good prop or some peice of crap that somebody carved on or cobbled up or a bad set up overall. PERIOD!!!

The GPS don't lie either and it puts pen and paper theory out the window. PERIOD.

[Ron Hill]

I'M ONLY STATING A FACT THE SMART PEOPLE ON THIS THREAD CAN TELL WHAT YOU ARE WEARING BY THAT ENDLESS STREAM OF BULL**** THAT YOU KEEP GOING ON AND ON ABOUT. HAVE YOU EVER BEEN IN A RACE OR RACE BOAT/ if you have prove it post pictures and speeds.Let us see how fast you can make a boat go.

I help several high schools with their Solar Race boat and three coleges with their solar race boats. I laugh, not openly, but one thing all these "KIDS" have in common is they have never driven a boat, never raced a boat, never been to a boat race and none of their teachers have driven a boat, or been to a boat race........But the colleges all have "COMPUTERS" to help them design boats. AND they all look about the same......thye look like submarines.

Chad and I had a "DISCUSSION" about my two motors, one prop theory. He said, one motor wasn't turning 7,200 RPM's....I never had a tach in the boat, so he might have a point, but I told him he was wrong.

I said, "Explain this. My OLD "C" Runabout ran 56 MPH on a good day. Same prop on my new boat ran 59-60 MPH. In my mind, my 30-H was turning 7,200 RPM's on both boats"

[pdt]

Mike go ask the other fellow to explain it to you.
because you will never belive me, even if I was standing on a stack of bibles with jesus Christ next to me backing me up.

[pdt]

ron you wrote

I said, "Explain this. My OLD "C" Runabout ran 56 MPH on a good day. Same prop on my new boat ran 59-60 MPH. In my mind, my 30-H was turning 7,200 RPM's on both boats" .....



how did you come to the idea of 7,200 rpms rons,

1/ did you just pick that figure out the air ?
2/ listen to the engine and could hear it was exactly 7200 ?
or
3? have a good idea due to the figures you had worked out with pitch ,gear ratio and speed reached ?

[champ20B]

I had a 15 X 30 on my V-8 Johnson than ran through the kilo at 118 MPH. At that time, we figured it was 110% efficiency. I concluded, that Mercury didn't include the CUP as part of their pitch.

Well then, you simply found that the figure given by the manufacturer wasn't right. It was inaccurate. The old pen and paper showed you that, so you went to see why it was!!

THANK GOODNESS FOR MATH (ESTIMATION FORMULAS)!!!!!!

[champ20B]

The GPS don't lie either and it puts pen and paper theory out the window. PERIOD.

What?????? No No No. One uses the formula to give a direct speed that is only "theoretical". One then takes the boat and records the ACTUAL SPEED ON THE "GPS". From these two speeds, one can see what the slippage is, or in Ron's case, if the pitch given is accurate or not. That's all it is and there is nothing wrong with it. Its a good thing!!

[champ20B]

In physics, a solid (ie; propeller) will displace a liquid (ie; water). Water is not stable material as a propeller in structure. Water will not stand up. It can be propelled or swam through but never tracked like solid ground. That is why 100% wont happen.

[HankFrazier]

in physics, a solid (ie; propeller) will displace a liquid (ie; water). Water is not stable material as a propeller in structure. Water will not stand up. It can be propelled or swam through but never tracked like solid ground. That is why 100% wont happen.
i have got a pretty good reputation when it comes to testing and tuning race boats and motors i do a lot of my own custom stuff. I also do a lot of custom work for other people.i have the fastest flat bottom aluminum boat that i have ever seen.and i have come to the conclusion that i am no where near smart enough to hold a conversation with pdt or champ 20b much less try to talk about how to make a boat go fast. I've only been doing it 35 years and as far as i can see ya'll can do in 10 minutes with pen and paper what it has taken me a life time to figure out.

[champ20B]

i have got a pretty good reputation when it comes to testing and tuning race boats and motors i do a lot of my own custom stuff. I also do a lot of custom work for other people.i have the fastest flat bottom aluminum boat that i have ever seen.and i have come to the conclusion that i am no where near smart enough to hold a conversation with pdt or champ 20b much less try to talk about how to make a boat go fast. I've only been doing it 35 years and as far as i can see ya'll can do in 10 minutes with pen and paper what it has taken me a life time to figure out.

I have respect for those of you out there who have dedicated years to the quest for performance on the water. It is from guys like you of which I have learned what I know. I dont want anyone to think I am just some young smart-elic commentator. Im only in my 30s, but I have dedicated years to speed boats as well. It is a family tradition of over 50 years. I also learned about engines and racing from a man who started racing in 1927 and raced till 1958. He was a graduate of the Curtis Wright aeronautical mechanic school in the 1930s as well. I have a certificate in machining and had brought many antique motors to life that are still running years later. As for my method of speed calculations, I don't use pen and paper........

I use a graphing utility calculator hand in hand with my GPS.....and that is as precise as precise can get. Work smarter, not harder.

[MWhite]

I have respect for those of you out there who have dedicated years to the quest for performance on the water. It is from guys like you of which I have learned what I know. I dont want anyone to think I am just some young smart-elic commentator. Im only in my 30s, but I have dedicated years to speed boats as well. It is a family tradition of over 50 years. I also learned about engines and racing from a man who started racing in 1927 and raced till 1958. He was a graduate of the Curtis Wright aeronautical mechanic school in the 1930s as well. I have a certificate in machining and had brought many antique motors to life that are still running years later. As for my method of speed calculations, I don't use pen and paper........

I use a graphing utility calculator hand in hand with my GPS.....and that is as precise as precise can get. Work smarter, not harder.

Your only in your 30s and u have dedicated years to speed to boats,, hell your still wet behind the ears!!!! and u learned about engines from a man that raced for 30 years,, how can u learn from a man that probably die before u was born!!!!! so how can that be, U and phil can calculate this and that and all the figures u wont to,but the gps will tell the truth and is going to tell me what i wont to know, i dont care how much prop slippage i have or will have,and i dont need know one to explain nothin to me eitheir,, so take your pen and paper theory else where.

[zul8tr]

What do suppose we did before gps? I tested huge, kept good notes and received real good set up and driving info from a lot of top runners: Harry Pinner, Marshall Eldridge Jr, Mark Hauptner and others. Used water pickup speedo in combination with a measured distance and a stop watch (IMO beats gps cause relative to the water), then a course on a small isolated lake in West Palm Beach with a stop watch to do the lap and a fair amount of theory mixed in there (hard to prevent that since my field includes hydro and aerodynamics).

Prop design was discussed alot with Harry who made all of mine, then tested the poop out of them and found what worked on the race course.

Harry would say "it's not how fast your boat is , it's how fast it goes around a race course and finishes".

I this thread close to the end?

[champ20B]

Your only in your 30s and u have dedicated years to speed to boats,, hell your still wet behind the ears!!!! and u learned about engines from a man that raced for 30 years,, how can u learn from a man that probably die before u was born!!!!! so how can that be, U and phil can calculate this and that and all the figures u wont to,but the gps will tell the truth and is going to tell me what i wont to know, i dont care how much prop slippage i have or will have,and i dont need know one to explain nothin to me eitheir,, so take your pen and paper theory else where.

Ok. here is your calculations! Mr.Renfro ( my mentor) was 13 when his parents got him into racing. He was born in 1914 as far as I know. I helped him in his outboard parts buisness fron age 16 (part time) till I was 31. If he were still alive, he would be 99 years old now. People do live to be older than that. I am "close" to 40 myself now and thats all I'm gonna say about that. Also, I grew up in the powerboat manufacturing INDUSTRY. Although I'm not taking part in it anymore as to persue other interests, I'm no newcomer in any of this stuff. I'm just trying to help people out with thier questions from time to time here if that is o.k with everybody. I enjoy doing things like that once in a while, thats all. I wasn't trying to be mean and cut anyone down here.

[HankFrazier]

Ok. here is your calculations! Mr.Renfro ( my mentor) was 13 when his parents got him into racing. He was born in 1914 as far as I know. I helped him in his outboard parts buisness fron age 16 (part time) till I was 31. If he were still alive, he would be 99 years old now. People do live to be older than that. I am "close" to 40 myself now and thats all I'm gonna say about that. Also, I grew up in the powerboat manufacturing INDUSTRY. Although I'm not taking part in it anymore as to persue other interests, I'm no newcomer in any of this stuff. I'm just trying to help people out with thier questions from time to time here if that is o.k with everybody. I enjoy doing things like that once in a while, thats all. I wasn't trying to be mean and cut anyone down here.
tO BE HONEST WITH YOU I NEVER CARED WHAT MY TOP SPEED WAS AS LONG AS I WAS FIRST ON RACE DAY. I CANT SEE WHERE THE WAY YOU CAL. SPEED WOULD BE VERY HELPFUL TO SOMEONE THATS TRYING TO GO FASTER THEIR ARE TOO MANY OTHER FACTORS THAT COME IN TO PLAY.

[champ20B]

tO BE HONEST WITH YOU I NEVER CARED WHAT MY TOP SPEED WAS AS LONG AS I WAS FIRST ON RACE DAY. I CANT SEE WHERE THE WAY YOU CAL. SPEED WOULD BE VERY HELPFUL TO SOMEONE THATS TRYING TO GO FASTER THEIR ARE TOO MANY OTHER FACTORS THAT COME IN TO PLAY.

Well, it's America. Anyone is free to do what they want. Im just putting my two cents out for seekers who look at these forums, that are new to set ups on boats looking for advise. As for me, if I'm going to bust my chops building up a good racer, putting what little hard earned money I have into it, I'm going to know my rig in every context including performance in efficiency. There could be an extra few % that I might get that wont just run in the race, but actually set a record. When I get going eventually, I'll aim high while setting up my new "B" superstock runabout. These formulas help me see "OVERALL PERFORMANCE" not just one or two things here and there. If I think I can get a few extra % out of the whole package, it could be hull, engine, setup, or prop. But bieng that the prop is the link to motion, that is the key of where the FIGURING STARTS. Checking hull, trying set ups: ect, comes with it all. I'll say no more. I'm outta here!

[MWhite]

Mike you do agree with me, but of course you just cannot bare to admit I am right.

come on mike lets put it to the test, see who's so wrong shall we.
what is the very maximum revs, gear ratio and prop size you get with your engine at the highest speed you get ? don't tell me the speed, just the ratio, prop, and rpm's.

don't forget I can only tell you its maximum possible, not actual as you will be a bit slower , though probably not by much.!!!!!!!!

you and your friends will probably already know these figures to the very finest detail.

ok,, around 7300 7400,, 1.83gear with a 16pitch fishing prop for starts, this isn't my racing prop that I use, so we'll get to that later, u don't know the heights I run my motor,, wether my props is 2blade 3blade are 4blade the weight of the boat,and so on,your the guru,, u tell me,, give it your best shot, keep in mind I already know the answer and I got people that can backup what im saying.

[pdt]

max possible attainable with these figures would be 61.27 mph at 7400 rpm. with a 1.83 to 1 gear ratio.

if the speed obtained is over 61.27 then the figures given are wrong, as this is maximum possible efficiency.
to get higher speed at those rpm's with this gear ratio would need larger pitch than 16 inch.

.

[MWhite]

max possible attainable with these figures would be 68.91 mph at 7400 rpm.

if the speed obtained is over 68.91 then the figures given are wrong, as this is maximum possible efficiency.
to get higher speed at those rpm's with this gear ratio would need larger pitch than 16 inch.

.
Ok now do the same thing with a 20pitch mercury racing cleaver just like the one in my picture at 7200 rpms.

[pdt]

20 pitch at 7400 rpm and 1.83 gear ratio would be max possible of 77mph

by the way I did have to correct the first speed.

[MWhite]

max possible attainable with these figures would be 61.27 mph at 7400 rpm. with a 1.83 to 1 gear ratio.

if the speed obtained is over 61.27 then the figures given are wrong, as this is maximum possible efficiency.
to get higher speed at those rpm's with this gear ratio would need larger pitch than 16 inch.

.
u did this with figure in the first one with 1.63 or 1.83 mind is 1.83gearcase

[pdt]

1.83 gear ratio.
the original post with 1.63 was typing errors
the post now has correct figures.. 61.27mph is maximum possible.

[MWhite]

max possible attainable with these figures would be 61.27 mph at 7400 rpm. with a 1.83 to 1 gear ratio.

if the speed obtained is over 61.27 then the figures given are wrong, as this is maximum possible efficiency.
to get higher speed at those rpm's with this gear ratio would need larger pitch than 16 inch.

.
Well u off alittle on the first one, but close 60.8 on gps with a fishing wheel is bout where it runs in fishing mode,, the second one is off a lot more.

[pdt]

ok so with the speed figures you gave for the first one, the rig is running at just 1.94% under maximum possible speed.
that means there is no chance of making that better with those figures if they are infact true ( if the prop is definitely 16 pitch) there are people spending millions to get this close.
but there ya go.

now what about the second one ?

7200rpm 20 pitch 1.83 gears = max possible of 74.52 mph. that's providing its 20 pitch.
if your over this speed then again the prop must have more pitch.

but if this is as efficient as the first prop you should be getting 73.07 mph

[pdt]

the efficiency of the 16 prop is probably a lot lot better than you might have thought.
to get a prop working that efficient is incredible, and even ron hill would love to be able to say his props can guarantee this on any boat.

[pdt]

ok
at 7200 rpm with 20 pitch its 74.52mph max possible

at 7300 rpm with 20 pitch its 75.56 mph max possible

[MWhite]

ok so with the speed figures you gave for the first one, the rig is running at just 1.94% under maximum possible speed.
that means there is no chance of making that better with those figures if they are infact true ( if the prop is definitely 16 pitch) there are people spending millions to get this close.
but there ya go.

now what about the second one ?

7200rpm 20 pitch 1.83 gears = max possible of 74.52 mph. that's providing its 20 pitch.
if your over this speed then again the prop must have more pitch.

but if this is as efficient as the first prop you should be getting 73.07 mph

wrong on the second one, phil. sorry bout that u got me running alittle faster than I can run on my ole fishing boat. by 3mph, so there u go your figures aren't always right.

[pdt]

if at 7300 rpm your doing 72.5 mph then you are running at 4.04 % under maximum possible. nobody could complain about that sort of efficiency.
anything under 8% efficiency on a race boat is very good, under 5% is something that many only dream of.

now you see that when someone gives figures like 10 or 15mph more than possible, they are either lying or the figures are wrong.

your boat is fantastic for its efficiency, not many are that good ..

my figures are not wrong, my figures only show what is only the mx possible. there is no way I or anyone else could know what speed below this max you can get.

you should be a very happy chappie with such low percentages,

[pdt]

I wonder what it would do with a mercury 22 pitch bronze 2 blade that used to be run on the old 85hp merc.

[MWhite]

if at 7300 rpm your doing 72.5 mph then you are running at 4.04 % under maximum possible. nobody could complain about that sort of efficiency.
anything under 8% efficiency on a race boat is very good, under 5% is something that many only dream of.

now you see that when someone gives figures like 10 or 15mph more than possible, they are either lying or the figures are wrong.

your boat is fantastic for its efficiency, not many are that good ..

my figures are not wrong, my figures only show what is only the mx possible. there is no way I or anyone else could know what speed below this max you can get.

you should be a very happy chappie with such low percentages,
I got many years of doing this, so formula and theory aren't always right here ok,,,, I've done lots of time testing and tuning and set up plays a major factor on the way a boat will perform as with a prop.,, u can have 3 of the same pitch props and the same diameter and 1 out of the three will be faster than the others, lots of things come in to play, the boat weight, the weight in the boat, wind, temperature, the motor height, tork, just to name afew,, u don't just go throw a motor on a boat and it runs this, I had to work to get it there. I use a gps (not a phone gps) and its pretty accurate, and my boat is a stock production 15/48 weldbilt boat not a race boat.

[pdt]

exactly
you have a boat that has took a lot to get it as perfect as possible..if someone went a bought a stock boat bolted on the same exact engine at same rpm's and just jumped in the
boat and ran it, it probably be 10 maybe 15mph slower.

the variables are what make it slower, not faster, you might get a day when the weather is very hot and humid and the boat is a touch slower, or waves on the river slowing it down etc.

but none of these things will make your boat faster, not a chance, its only by making the percentages lower than speed is gained with the same rpm gears and prop.
if someone come along and says he has same engine at same revs with same size prop and is getting 80mph plus, you know its not possible with the given figures.


by using a set of figures to start with and charting exactly what you do, this helps to know what props for certain conditions as well to race with.
you might have a prop that's 4mph slower on a hot smooth day,but its the fastest when in rough water etc, like tyres on a race car..

[Nason]

Well u off alittle on the first one, but close 60.8 on gps with a fishing wheel is bout where it runs in fishing mode,, the second one is off a lot more.

Mike you been playing with that junk fishing prop, You gained .8 mph since last time I drove your boat....

[MWhite]

Mike you been playing with that junk fishing prop, You gained .8 mph since last time I drove your boat....

no,, Its always had some more, just didn't show it to u,, and i still got alittle more.

[ima75man]

all this trailer racing going on. my boat runs 57 mph in a short distance turns lots of rpm's.lot of 80 mph boats can't beat me.i don't race gps's. i race boats.tachs and gps's are great tools, but if i lose i know i got to get faster.i dont race numbers , i race against boats.anybody got a video of some gps's racing each other.. out

[pdt]

oh poor ima75man
only 57mph ? what happened to your fast stuff ?
i thought you were the man on that river with your omc super-rudes and frankenmerckillers.
you aint surely admitting those sabine boys are 50% faster with them black tiller handles surely ;)

[ima75man]

i surely ain't guna admit nothing, maybe i got the numbers wrong. maybe it's 75 mph.lol i ain't telling nothing. just for fun racing is what happening around here. like to thank brf's for making it possible to meet so many super nice racers, i learned there's more to racing than winning. you can't by friends but you can buy a winning raceboat.lol i have one for sale.. lol