help with new boat setup

[chris3298]

I'm not sure where to post this at on this forum so here goes. I've got a 15x52 alweld Vee La aluminum boat which is really a V bottom all the way to the back of the boat not just a semi V in the front like some aluminum boats. I have a 2011 Tohatsu 50 TLDI shortshaft stock aluminum prop 11.1x14 I think. This boat was bought for fishing and well to play with and go fast. The boat has a 17 inch transom aluminum trim tabs welded to the boat that came standard with the boat, it has a deck at the bow and a bench seat in back.

I took the boat out for the first time Saturday with the motor completely down on the transom and motor trimmed fully down boat ran great at full throttle with my dad who weighed about 250 sitting on the deck on the bow. Absolutly no porpoising. When I went to trim the engine up not very much it started to porpoise. I thought you wanted to be able to trim the motor up some so I could maybe get more speed out of it.

I'd just like to get more speed out of the boat and would like to know what advice can yall give me?

I forgot to add I have a battery just behind the rear bench seat and the gas tank I have now mounted far forward. I did notice that one of the trim tabs was bent up while the other was level with the boat. I bet it was bent during shipping. I made sure they are now both level with the bottom of the boat. I also raised the engine up two bolt holes to try and get the cavitation plate level with the bottle of the boat and it is but of course I trimmed the motor up so that cavitation plate was level with the bottle of the boat in reality I will probably have to have the engine fully down tomorrow to run the boat and keep it from porpoising so in a sense the half the cavitation plate will be below the bottom of the boat because I will have to run the motor fully down.

So what can I do to achieve more speed?

Thanks
Chris

I have probably confuses the hell out of yall but want to give you as much information as i can to help me have a better setup.

[zul8tr]

Can you post some pics of the rear with trim tabs and engine. Need to see the size of the tabs.

Based on the porpoise operation you note I would trim the engine out so the prop shaft is level with the bottom and note the ride, Then from there adjust the trim tabs angled down to force the bow down. Unfortuanately you state the tabs are welded so a hammer is the tool. If that provides success then raise the engine on the transom and check the ride in the straights and the turns. Generally in turns an engine to high will cavatate.

Experiment is the only way and keep notes.

Tell us the results

[chris3298]

Thanks so I should probably drop the engine back down all the way on the transom and go from there adjusting the tabs.
I don't have a digital camera but will see if I can take a picture with my laptop this afternoon

Ok now gotta figure out how to post a picture

[chris3298]

The rear and sides of boat, sorry if the image isn't to great if it is hard to see I will try taking my boat out the garage for better lighting. I dropped the motor all the way down like you said and I used two pieces of 2x4 with 2 C clamps and bent the trim tabs more level with the bottom maybe even a little past level.

[zul8tr]

First place engine flat on transom with no shims then adjust the engine prop shaft level with the bottom and run it and get a base line reading of performance, Do you have a speedometer and tachomerter?

Those trim tabs look rather small and they might need to be increased and made adjustable without bending.But try them as they are by bending.

[chris3298]

Just back from the river, first thing i noticed is well i may have bent those trim tabs a little to much past the level part of the bottom and noticed more spray. Well the thing got on a plane quick and the nose was down was thinking dam maybe i bent them to much, ran WOT and was thinking dam my fat dad in the front it seemed faster then i forgot to trim the motor up, I did with just very small burst of the button ran like that a while till I got use to it. I then said ok time to trim and get this motor level and well it was tuff to tell I think I was pretty close to being level meaning triming the motor up. I wish I would have brought a tape measure to then measure the bottom of the tiller handle to the seat and make this measurement again when on dry land to see just how level the motor was and forgot the dam gps to but the motor was trimmed up alot more then the first time out. I felt like i was a lot faster triming it up, there was times that it was porpoising but was able to get on the throttle and work the porpoise out. Today was very windy and not a good day for fishing but barely good enough for testing the boat on the river.

Something I noticed was when trimmed up and wot it didn't feel like much of the boat was running in the water, at times the wind or current seem to catch the boat and want to move me over, it felt like, the back end was very loose meaning felt like not much was in the water but felt dam fast. Almost like it was easier to move the tiller but at the same time very easy to get out of control.

I do have a question about the tabs, a friend of mine here in Louisiana had a custom built boat much heavier but the rear of the boat looks like the way it was made they extended the bottom plate so he had about 2-3 inch lip as like a trim tab like mine but was across the entire back of the boat. There was a small cut out for where the lower unit was. I'm just curious to know why this was done and in my case would it help it any for those trim tabs to be longer?

Another guy with same setup as me on another forum has real porpoising issues but mine don't seem to be to bad I hope.

Forgot to add the motor was fully down on the transom this run. No tach but have seen a brand called Tiny tach which is a digital tach but not sure if it will work on this motor. Can you recommend a tach?

Thanks
Chris

[zul8tr]

Sounds like progress. Need to bring that gps next time. Have you been keeping notes? The tiny tack is OK just inquire with them if the model they offer willl work on your engine. They used to have a series of different models but now they offer one that has settings for several different engine types. I have the older version 1C that was for a specific 2 cycle engine that works on my 1973 Merc 25ss CD ignition 2 cylindere and the yamato Y80 2 cycle 2 cylindere standard point and condenser ignition.

As far as the bottom extension you note forget that and stick with the tabs and experiment with bending. If that gets you running right you are set, If the tabs were larger in both directions that would provide more surface area for trim most likely at less of a down angle to achieve that same effect as the smaller tabs. However if the tabs were adjustable they would be easier to note the position and a finer adjustment allowed.

The next phase is to start raising the engine on the transom and adjust motor angle and tabs to suit the new height.

Keep notes

Do you know the prop diameter and pitch and engine lower unit gear ratio?

[chris3298]

I have not kept notes but really this is truly the third time i been out in this boat. Second time i moved that motor to high and was moving to fast in the adjustments.

I was gonna run today but it is raining, will have to tomorrow. I took the advice of someone on another forum and got my boat as level as I could with a level and then tilted the engine up to where the level read level on the cavitation plate and I made two marks so when I am back out there and have trimmed my motor up as high as I can go to the point it doesn't porpoise i can then stop and see if the marks line up and if the motor is level.

Depending on if the marks line up I will either bend the tabs down more or like you say raise the motor up one hole. Speed is definitely a slow learning process I realize now.

Tohatsu website says the gear is a 1.85:1 the prop is an aluminum 11.1x14 this prop came with the motor. I noticed yesterday this boat takes off really well if I can tame the porpoising as I raise the engine I think I could maybe get a good bit of speed out of it, I hope we shall see.

I did put a straight edge under the boat now it isn't as perfectly flat as I would have liked but the boat seems to have a little bit of a hook. I understand it's tuff to get a boat flat this thin of aluminum and aluminum likes to warp like mad when you weld it.

Out of curiousity anyone here on this forum ever build there own aluminum boat? This is something I'd really like to do. A boat built for speed :)

Thanks
Chris

[zul8tr]

As a point of reference with a 14 pitch prop and a 1.85 gear ratio here are some theoretical speeds

at 5000 rpm about 36 mph
at 5500 rpm about 40
at 6000 rpm about 43
at 6500 rpm about 47

Calculated from MPH = 14 pitch in inches x RPM / (1056 x 1.85 gear ratio) = RPM / 139,5

These speeds assume no slip and that is impossible so expect somewhat slower mph by about 10% of those calculated..

The hook in the bottom is like some down angle on the trim tabs it will put the bow down somewhat, Unfortunatly a hook is not desirable.

Keep working on it

[chris3298]

Thanks for the information, I must say this bot is 10 times better then what i had. I had before was a J14 carolina skiff it weighed probably about 550 and had to two rocker and one really bad hook. That was the worst boat I ever had this boat is just about perfect compared to that one haha.

I guess really the only way if you want to go fast is to build your own. I've learned my lesson you want it done right you gotta do it yourself.

[chris3298]

zul8tr,

Today made a run, with the motor all the way down on the transom and trimmed up to just before level on the cavitation plate according to my marks i made on the motor I was able to top out on GPS at 39.1 mph. I tried many many times to go faster and this is all it would do, which really doesn't seem to bad with a stock crappy aluminum prop.

Motor trimmed all the way down it ran 34.3 mph really is a big difference once you get it trimmed up.

I tried trimming the motor up to where i had made a mark on the motor to give me an idea of the cavitation plate was level. i couldn't quite go that high well I could but was experiencing some porpoising and I was able to ride WOT like that it wasn't out of control or anything.

Where I did have the motor at just before I was level at my mark I must say that the cavitation plate was dam close to running level according to my marks.

Do you think I should try bending the trim tabs a hair more down or just go up one hole with the motor? I'm tempted to bend them a spec more and try it out to get that motor running a spec more level. I was really close to though to my marks.

Hell my marks could even be off a spec because what I thought was level in my garage just didn't seem like that bow road that high in the water.

What are your thoughts?

Wanted to add this motor suposily can run at 5150-5850 max rpm according to the website on the motor/

Thanks
Chris

[JohnsonM50]

zul8tr,

Today made a run, with the motor all the way down on the transom and trimmed up to just before level on the cavitation plate according to my marks i made on the motor I was able to top out on GPS at 39.1 mph. I tried many many times to go faster and this is all it would do, which really doesn't seem to bad with a stock crappy aluminum prop.

Motor trimmed all the way down it ran 34.3 mph really is a big difference once you get it trimmed up.

I tried trimming the motor up to where i had made a mark on the motor to give me an idea of the cavitation plate was level. i couldn't quite go that high well I could but was experiencing some porpoising and I was able to ride WOT like that it wasn't out of control or anything.

Where I did have the motor at just before I was level at my mark I must say that the cavitation plate was dam close to running level according to my marks.

Do you think I should try bending the trim tabs a hair more down or just go up one hole with the motor? I'm tempted to bend them a spec more and try it out to get that motor running a spec more level. I was really close to though to my marks.

Hell my marks could even be off a spec because what I thought was level in my garage just didn't seem like that bow road that high in the water.

What are your thoughts?

Wanted to add this motor suposily can run at 5150-5850 max rpm according to the website on the motor/

Thanks
Chris
Reading along Id say your making good progress. I agree about notes, you can have progress in leaps & bounds but once near potential it gets harder to figure & you might even lose some if you don't document: setup, speed, R's & conditions. If you go for a better prop at some point it will be worth getting the most out of it -if ya wanna go fast:D
My experience with aluminum boats has it that just passed the point where it begins to porpoise at full speed will likely be where your fastest straight line speed is. Not the best for turning tho. Here's a pic of some easy to make trim tabs:
http://i35.photobucket.com/albums/d151/mes355/DSCN0297.jpg
You'll end up running them fixed but can move em any time. Those in particular are mounted 1/4" up from the bottom so act like a step for less drag. At the rear of the tab for that boat they work best at about 1/8" up from the bottom. Good Luck

[chris3298]

Reading along Id say your making good progress. I agree about notes, you can have progress in leaps & bounds but once near potential it gets harder to figure & you might even lose some if you don't document: setup, speed, R's & conditions. If you go for a better prop at some point it will be worth getting the most out of it -if ya wanna go fast:D
My experience with aluminum boats has it that just passed the point where it begins to porpoise at full speed will likely be where your fastest straight line speed is. Not the best for turning tho. Here's a pic of some easy to make trim tabs:
http://i35.photobucket.com/albums/d151/mes355/DSCN0297.jpg
You'll end up running them fixed but can move em any time. Those in particular are mounted 1/4" up from the bottom so act like a step for less drag. At the rear of the tab for that boat they work best at about 1/8" up from the bottom. Good Luck

Thanks I wasn't sure if anyone else would reply, heck with over 200 views and two people now chiming in I really do appreciate it. This boat is my fishing boat but I do like to go fast.

You're right tonight I will start taking some notes for what I have done so far, I'm not sure if I should raise the engine up one more hole or try and bend the tabs a spec more?
I'm leaning towards raising the motor up one hole on the transom because I feel the tabs are bent pretty close to equally and I'd hate to bend them more and end up screwing up and loosing the progress I already have.

I think I'll go up one hole on the motor because i can easily come back down if i need to.
I may do that tonight and try again tomorrow and see what happens.

Thanks for posting that homemade trim tab I may end up going to that later on. This style trim tab how long is it across?? and should I maybe even make them wider?
I see the plate looks like maybe aluminum, is the hinge stainless??

I will go with another prop down the road but kinda want to experiment and get the most that I can with the setup and it's good learning experience.

I'd like to know could I see 50 or 55mph from this boat and motor setup? I know this motor can't be hopped up because it is fuel injected I'm sure there is more that can be done with the carb version and who knows later on I may want to look for the carb version of this motor or maybe a mercury 40 to play with.

I have to say though this speed stuff is addicting:D

Thanks
Chris

[JohnsonM50]

Thanks I wasn't sure if anyone else would reply, heck with over 200 views and two people now chiming in I really do appreciate it. This boat is my fishing boat but I do like to go fast.

You're right tonight I will start taking some notes for what I have done so far, I'm not sure if I should raise the engine up one more hole or try and bend the tabs a spec more?
I'm leaning towards raising the motor up one hole on the transom because I feel the tabs are bent pretty close to equally and I'd hate to bend them more and end up screwing up and loosing the progress I already have.

I think I'll go up one hole on the motor because i can easily come back down if i need to.
I may do that tonight and try again tomorrow and see what happens.

Thanks for posting that homemade trim tab I may end up going to that later on. This style trim tab how long is it across?? and should I maybe even make them wider?
I see the plate looks like maybe aluminum, is the hinge stainless??

I will go with another prop down the road but kinda want to experiment and get the most that I can with the setup and it's good learning experience.

I'd like to know could I see 50 or 55mph from this boat and motor setup? I know this motor can't be hopped up because it is fuel injected I'm sure there is more that can be done with the carb version and who knows later on I may want to look for the carb version of this motor or maybe a mercury 40 to play with.

I have to say though this speed stuff is addicting:D

Thanks
Chris
Replies, Its not an unfriendly thing, more a probable concern for your well being in as much as hopping up a standard boat being dangerous. When it comes to going fast of course the danger meter goes up just as fast or more. That said you are working with a motor within your boats capacity right? So reaching its potential is good experience. Just be careful, wear the vest when you intend to play with the speed, a helmet if it gets really fast. 50 is kind of a milestone for non racing boats, especially those w/o tons-o-hp. To reach it at all would be surprising.
The trim tabs are 1/4 aluminum, The continuous hinge is SS. I threaded & loc-tite-d the hinge to the aluminum & ground the screws flat on the bottom. The turn buckles are from Loews, the mounts are just junk I had around. They are about 5" wide & 4" long. The boat is 11'8" so somewhere in proportion should help. If you over porpoise the boat be prepared to start repairing leaks :eek: the pounding takes a rapid toll :rolleyes: Good Luck
"The speed stuff", If the bug bites hard enough, consider racing. There you get to go for it knowing that tow boats, water rescue, & EMT's are there for you. At that point the replies to your requests will multiply.
It would seem that you are young, maybe even a minor?, please take no offense to that, just to say that if you are be sure your Dad knows what you're doing :cool:

[chris3298]

I was kinda thinking the same thing that people don't want to say because of the danger factor. I always wear a life jacket when in the boat by myself or with others, anyone who rides in my beat wears a life jacket if not they don't ride, not wearing a life vest you're an idiot plain and simple. I wear that safety cord hooked to my life jacket or wrist at all times again you're an idiot if you don't.
I have a friend who won't wear one, I know he can't swim that great, i'm just waiting to get a call someday from his mother saying he's dead but thats his choice. Preaching doesn't do any good about safety with him.

The boat is well rated as a commercial boat, if i ordered it as a recreation boat it would have had a sticker that said max HP would be 40 so I'm 10 over which don't feel that is a lot.

Sorry if I sound young I have had many times people think I'm 10 years younger then what I look, I'm 32. DAD didn't buy this boat and motor only thing he did was give me a trailer for it that is probably older then me which I had to go through and replace every bolt with stainless and buy a new axle. I probably should have bought a trailer for all I had to do to it. So a minor yeah I'd say I'm a minor at heart, all my friend are married and having kids and I'm just looking at what is the next toy i can buy hahaha

There is a place that does racing down here in Louisiana, I think it's in like Alexandria Louisiana which is good drive aways for me, it wouldn't make much sense in getting into it for what I'd have to drive to race.
Bogalusa Louisiana there is a boat club which does some drag racing now this I'd really like to go and participate in there about 20 miles away if that.

Thanks
Chris

[JohnsonM50]

I was kinda thinking the same thing that people don't want to say because of the danger factor. I always wear a life jacket when in the boat by myself or with others, anyone who rides in my beat wears a life jacket if not they don't ride, not wearing a life vest you're an idiot plain and simple. I wear that safety cord hooked to my life jacket or wrist at all times again you're an idiot if you don't.
I have a friend who won't wear one, I know he can't swim that great, i'm just waiting to get a call someday from his mother saying he's dead but thats his choice. Preaching doesn't do any good about safety with him.

The boat is well rated as a commercial boat, if i ordered it as a recreation boat it would have had a sticker that said max HP would be 40 so I'm 10 over which don't feel that is a lot.

Sorry if I sound young I have had many times people think I'm 10 years younger then what I look, I'm 32. DAD didn't buy this boat and motor only thing he did was give me a trailer for it that is probably older then me which I had to go through and replace every bolt with stainless and buy a new axle. I probably should have bought a trailer for all I had to do to it. So a minor yeah I'd say I'm a minor at heart, all my friend are married and having kids and I'm just looking at what is the next toy i can buy hahaha

There is a place that does racing down here in Louisiana, I think it's in like Alexandria Louisiana which is good drive aways for me, it wouldn't make much sense in getting into it for what I'd have to drive to race.
Bogalusa Louisiana there is a boat club which does some drag racing now this I'd really like to go and participate in there about 20 miles away if that.

Thanks
Chris
Cool, Drags would be fun. Im I took my hydro to drags & had a blast. There's no real close racing here either but close enuff, 20 miles aint bad.

[zul8tr]

If you want to hit 50 you are going to need rpm in the 6900 - 7000 rpm area and that is going to be difficult to do on your alum boat with the present engine and prop. Your engine might not take 7000 rpm for extended time??? Your present prop even lifted high would probably still limit the engine rpm but you can try to go higher on the transom before trying different props. I think it will definately take a smaller diameter and greater pitch prop with the engine really lifted high on the transom so that the prop shaft is close to the bottom to get the 7000 rpm area.

So far with the set you have you are close to the speed estimate I made at a prior post for the 5500 rpm range at about 39 mph so keep going and don't forget the notes. You still need a tach for rpm..

[chris3298]

Wow I know this motor won't run that high in rpm I'm sure the rev limiter would kick in. We'll just have to see what happens in the future. I'll keep going and see what happens though but you're right I need to shoot a email to tiny tach and see if that will work on this motor. I'm keeping notes now i have written down what I have done now so far.

Raised the motor up one hole last night gonna go get some gas and try it out again today.

Chris

[zul8tr]

Looking at the photos your engine has the water pickup screen about half way between the prop shaft and the anti-cavitation plate. So you will be limited to how high you can raise the motor before water starving the cooling. As you raise up take note of the cooling water discharge when up on plane. My visual guess is you can raise the motor so the anti-cavitation plate is about 3" above the bottom. You will also know if you are too high because the boat will not plane over and the prop will cavitate. This alone might be the limit with your hull and motor. As you raise the engine the prop will free up and engine rpm will increase and you could run out of prop pitch i.e. not enough pitch. Then a different prop is needed. Testing will reveal all of this

[JohnsonM50]

Ive found a standard prop to fail at traction before the flow was interrupted by height but each rig being different that needs to be watched. Most motors would scorch pretty fast run hard w/o water. :mad:

[chris3298]

Went out today and was able to move the engine up one hole like i said and my speed was 37.5 mph on GPS. I could hear the engine running a little higher in rpm's which I must say the engine did just sound better then when the motor was all the way down. Obviously I guess I would need a different pitch to be able to bite more. Water pressure was fine, it started porpoising the same as it did yesterday when I was really trimmed up high so there was no difference there.

I may just move that engine up a little higher for the hell of it although I know it will probably loose more speed and want to slip/cavitate even more but at least I will be able to see if it will get on a plane and will I still have good water pressure for cooling.

I should be able to move this engine much much higher up if i were to go to lower water pickup but I'm not sure about how well those things are, from what I understand I think a lot of bass boats run that lwp for fishing in such shallow water. I do have times I fish in shallow water so it could maybe benefit me for fishing.
I'd like to hear your thoughts on the lwp, goods and cons?

First thing is first is finding a tachometer that will work with this engine to see where I am at.

Something I'd like to ask yall which probably maybe some have heard of this guy. There is a guy literally 10 minutes from my house his name is Glen Hopkins, www.hopkinspropeller.com
This will be the guy I'll go to for a prop when the time comes. Just would like to know if anyone had heard of him and is he that good like I have heard from the few around here?

[JohnsonM50]

Went out today and was able to move the engine up one hole like i said and my speed was 37.5 mph on GPS. I could hear the engine running a little higher in rpm's which I must say the engine did just sound better then when the motor was all the way down. Obviously I guess I would need a different pitch to be able to bite more. Water pressure was fine, it started porpoising the same as it did yesterday when I was really trimmed up high so there was no difference there.

I may just move that engine up a little higher for the hell of it although I know it will probably loose more speed and want to slip/cavitate even more but at least I will be able to see if it will get on a plane and will I still have good water pressure for cooling.

I should be able to move this engine much much higher up if i were to go to lower water pickup but I'm not sure about how well those things are, from what I understand I think a lot of bass boats run that lwp for fishing in such shallow water. I do have times I fish in shallow water so it could maybe benefit me for fishing.
I'd like to hear your thoughts on the lwp, goods and cons?

First thing is first is finding a tachometer that will work with this engine to see where I am at.

Something I'd like to ask yall which probably maybe some have heard of this guy. There is a guy literally 10 minutes from my house his name is Glen Hopkins, www.hopkinspropeller.com
This will be the guy I'll go to for a prop when the time comes. Just would like to know if anyone had heard of him and is he that good like I have heard from the few around here?
I have a Hopkins 2 blade, It was my fastest runabout prop for some time till I got several others. Last summer I tried it along with my latest fastest 3 blade cleaver prop on a hydro & it made 1 pass at 1 mph under & the next the same speed. The cleaver made 3 passes all the same so is only ahead by consistency.
The catch is to get it right when you buy it, I've found that a stainless prop of the same #'s as an aluminum will be a little faster & grab better, SS being about 5x the strength can be made into a thinner bladed prop. Then to consider whether or not you by a surface drive type prop. This is where the LWP is needed. Things change when you go there, the boat may not go well from a stand still & need to be rev'd to get over the hump- onto plane. Most racing hydro's & runabouts have this drawback unless.. you get a drag prop.
It would take more snagged debris to clog your stock pick ups than a low water up front but Ive been lucky & never had it happen. Here's a trick Ive used but would be different for your motor:
http://i35.photobucket.com/albums/d151/mes355/DSCN0363.jpg
Plumbing this into your motor just under the pump & checking out whether or not it works with your stock pickups left open [might have to restrict or even close them] last but not least make sure it gets the volume needed. Or maybe better to do a nosecone deal? Whatever tho it needs to be checked out before run. If it has an indicator stream [pisser] you could run a tube from that up in front of you & off the side so you can see it as you go..it stops:eek:- you stop;) As far as raising the motor goes 'yes' to a point it will slow down & rev like crazy if too hi, more about the right height than up.

[shenders]

Chris.
If you are 10 min. from Hopkins then you have it made. Hopkins has made some of the fastest wheels in racing over the years. His father started the business back in the 40's I think. Glen is a good prop man and can get you dialed in. I think he will go down to the river with you and help you get set up.
Of course it may cost a little, but speed cost money, so how fast do you want to go.

Stan Henderson

[chris3298]

Thanks JohnsonM50 I could really see how that lwp would help me in some of the places I fish which is shallow but pretty grassy though so it may have a problem getting stopped up.
I seem to always be paddling for a while till i can get out to deeper waters which is aggravating and I see other who seem to just motor on out either they don't care that there motor is dragging or maybe they have this lwp.
I seen a video on youtube who had this pisser tube extended so the driver could see it pissing and that makes sense because this boat was an inflatable and used for racing, i'm sure there catching air a lot and don't want to take the chance of messing there motor up.

Stan, I went down to Glens shop one day when i had my other boat and thought I wanted a prop told him what the boat was doing. He put a straight edge and told me that selling a prop to me would do nothing it was the Hull that was the problem either sell it or try fixing it.
I was gona try fixing it then realized it was better to sell it, so I did. I was just curious to now if anyone here had heard of him and gosh for people all around the country to know this guy he must be pretty dam good. I left that day feeling like when i get another boat I oh it to this man to definitely buy a prop from him.

I talked to my dad about this one time and he said he had worked with Glen way the hell back in the day when they were teenagers and from what he remember and heard this guy was a good racer and good prop builder. Super friendly guy probably one fewest people around that would tell you the truth about your boat and not try and sell you junk.
I guess I'll need to save some money up now and go see him and see what he can do for me.

[chris3298]

Well after a while of fishing and boat riding I have decided to take yalls advice to now start looking into a new propeller for my motor to go faster. I ordered a new Tohatsu Tach which I hope will be coming in on Monday. I will be sending an email to the guy Alan over at Tohatsu who was willing to walk me through how to make a wiring harness and how to hook it up to my motor. I guess after I get the correct rpm readings I'll take this info to Glen Hopkins and see what is the best and fastest propeller for my setup.

I would like to try a cleaver propeller, from what i have read and sending pm's to different members here this is a prop I'd like to try. Seems like this prop is best used with a lower water pickup but i think there is a couple of members here who use it without the lwp and must be happy with it. So I think this is what I want to try.

The other day i was looking at my lower unit and notice the two side water pickups on the lower unit have what I thought was 5 little slits on each side to pickup the water, after close inspection I notice that 2 of the slits on each side were basically a dummy slit meaning when i looked really close those 2 slits don't even let the water in. So this tells me I could lift this motor up pretty high possibly before I starve it of water which I guess this acts like some have said putting a piece of tape to block off two holes.

When the Tach comes in I guess I will see where i am at now with the engine height and keep raising the motor till either the prop slips so bad that it won't get on a plane or till the point I still have good cooling and take my readings to Hopkins.
I'll keep you updated in my finds.

Chris

[JohnsonM50]

Per my previous post "It would take more snagged debris to clog your stock pick ups than a low water up front but Ive been lucky & never had it happen." That luck changed & I have picked up debris. Instead of cooking the motor tho it cooled it very quickly, the plastic wrapped prop & caused the boat to spin out, the fin stuck & over it went.

[chris3298]

Per my previous post "It would take more snagged debris to clog your stock pick ups than a low water up front but Ive been lucky & never had it happen." That luck changed & I have picked up debris. Instead of cooking the motor tho it cooled it very quickly, the plastic wrapped prop & caused the boat to spin out, the fin stuck & over it went.

I'm confused of what happened, you caught a trash bag in the prop and spun out?:D

[JohnsonM50]

I'm confused of what happened, you caught a trash bag in the prop and spun out?:D Yes, The boat it happened in is a flat bottom with a bottom fin, suddenly going sideways rolled the boat. Someone warned me when I got into this go fast boating stuff to be extra careful when I got fast... that & even sooner I'm thinkin cause ya never know.

[chris3298]

Yes, The boat it happened in is a flat bottom with a bottom fin, suddenly going sideways rolled the boat. Someone warned me when I got into this go fast boating stuff to be extra careful when I got fast... that & even sooner I'm thinkin cause ya never know.


Oh ok yes I have seen boats like this with the fin on the hull, I guess it helps with control in the turns. Yes now that i'm wanting to go faster I am realizing now i need a better life jacket which I'll be heading to bass pro here soon and getting a better one. I need new ones my current one is about 15 years old, it's probably time. :)

[chris3298]

Made two runs to the river today, First run I had the new Tohatsu tach hooked up and now realize this I'm checking the rpms with the motor raised just one bolt hole and my rpm's were about 5300. Second run I then went back home raised the motor to the third hole and was able to then get a solid 5400 rpm's maybe a spec more, Cooling was fine I kept looking back to make sure and it was good. Did notice two little cool rooster tails shooting upwards off the cavitation plate.

I really didn't notice any drop in speed going up to the third hole although didn't have my gps with me. I did notice looking back though there wasn't as much as a wake like before when I was only up on the second hole. Didn't hear any sounds like the prop was cavitating or anything.

I think I can go up to maybe the last hole but will really have to watch and see if it ends up sucking air and loosing water pressure, thought about putting a piece of tape at the top to holes even though there not open just to make sure it doesn't suck any kinda air.

I realize now a Jack plate is probably better at this stage I could probably run a little higher then on the last bolt hold and still be having good cooling and hopefully more speed

What you guys think? try a jack plate now? or go up to the last hole?

The motor needs to run at 5850 is what the manufacture says I was told it may even run a little higher that around 6100 is probably when the rev limiter will kick in.

prop used is 11x14.1 almost like i need to go down in the number which don't want to I want to go faster.

[zul8tr]

Made two runs to the river today, First run I had the new Tohatsu tach hooked up and now realize this I'm checking the rpms with the motor raised just one bolt hole and my rpm's were about 5300. Second run I then went back home raised the motor to the third hole and was able to then get a solid 5400 rpm's maybe a spec more, Cooling was fine I kept looking back to make sure and it was good. Did notice two little cool rooster tails shooting upwards off the cavitation plate.

I really didn't notice any drop in speed going up to the third hole although didn't have my gps with me. I did notice looking back though there wasn't as much as a wake like before when I was only up on the second hole. Didn't hear any sounds like the prop was cavitating or anything.

I think I can go up to maybe the last hole but will really have to watch and see if it ends up sucking air and loosing water pressure, thought about putting a piece of tape at the top to holes even though there not open just to make sure it doesn't suck any kinda air.

I realize now a Jack plate is probably better at this stage I could probably run a little higher then on the last bolt hold and still be having good cooling and hopefully more speed

What you guys think? try a jack plate now? or go up to the last hole?

The motor needs to run at 5850 is what the manufacture says I was told it may even run a little higher that around 6100 is probably when the rev limiter will kick in.

prop used is 11x14.1 almost like i need to go down in the number which don't want to I want to go faster.

If your tach is accurate first go up higher w/o jack plate (less costly approach) and note the rpm results bring the GPS so speed is measured , w/o that results are not complete.

If still below the rpm target you need to go to less pitch. Less pitch does not necessarily mean less speed because the rpm is increasing.

based in your numbers if rpm is 5400 then your est speed with no slip
= 5400 x 14/(1.85 x1056) = 38.7 mph
if you had GPS speed slip can be calculated

Example if pitch is reduced to 13 and rpm can get to 6100 with jacking and trim (just an example) then;

estimated no slip speed = 6100 x 13/(1.85 x 1056) = 40.6 mph, up a bit

Note these are made up numbers but you get the idea.

Test and take notes on gps speed and rpm so we have a solid point of reference to calc slip and other.

There might be some benefit to reduce the diameter and keep the pitch but if the hull is heavy this will go against you to plane especially if water skiing is to be done. For pure straight line speed runs the smallest diameter and largest pitch that will plane the boat, reach the rpm and max speed target is what you want. However the boat may not turn worth a crap, so you have to decide what you want. There is only so much you can extract :eek: from the boat and motor for the hp and weight that you have.

[chris3298]

thanks zul8tr I'll probably raise the motor again and go tomorrow and see what happens and will bring the gps.


UPDATE,



I went back to the river again, this time the motor lifted to the 4th hole and the rpms was really just a spec over 5400 rpm's it wasn't much difference it seemed... cool little rooster tail went higher making you think you're going faster but not really :) I think the motor could go maybe another inch or inch and a half before i end up with a serious cooling problem. I was nervous this was to high but after putting a straight edge it really wasn't high enough.

My speed was 35.8 mph with the motor all the way up. Tomorrow gonna go do some fishing and will lower the motor back down a hole and see what my mph is from there.

I did notice some times the prop was slipping more when I was running WOT now i would think if it was slipping I'd get more rpm's correct? but they pretty much stay just a hair over 5400 rpm's

Started wondering how accurate this tach is but this is the tach from Tohatsu and it's brand new and is for this motor. I wanted to go with this tach rather then the tiny tach hoping it would be more accurate, no doubt though going higher up on the motor it does just sound better for sure and I would think the tach must be about right because it does have a rev limiter and have not heard it kick in yet on the motor so maybe the tach is fairly accurate.

Now what? go with a jack plate and maybe get the rpm's a little higher and then go see Hopkins about a propeller or what? I know of people who just go see him right away with out even testing to see what rpm's there motor is running but I would think it is important to do this so you're helping him and yourself of getting everything you can out of that prop. There not cheap.

Thanks for all the help everyone, I decided to kinda keep this thread going in hopes it may help others who are joining the forum.

Forgot to add I want straight line speed is what I'm after, my knee boarding days are over.

Chris

[chris3298]

Went with a power tech 10.5x13 NREB prop it turns 5500 rpm's and with a lot of porpoise I was able to get close to 5550 at 37 mph max speed.

I was trying for 5850 rpm's, aluminum 11.1x14 prop was a max of 5400 rpms at 36.2 mph

Thinking of trying maybe a 11 pitch prop only because someone on another forum has EXACTLY the same boat and motor setup Same brand boat and motor and all and he has this prop but reworked to a 12 pitch and cup added so it wouldn't porpoise so much and turned 5600-5700 rpm's This prop does porpoise more for sure.

Also notice the dang motor wanting to turn the boat more to the right but maybe this is because I had 100 rpm's more and it as the torque doing it.

Gonna go see Hopkins next week sometime and see what else we can try

[chris3298]

ended up bring my 10.5x13 prop back to Hopkins and I decided to keep this prop but let him cut the blades for my rpm's which I was able to get exactly 5850 or even a spec more. Forgot the GPS again so not sure of speed, it did feel faster though. Trying to work this dam porpoise thing out but i think if i can get this worked out so that I don't have to bend those trim tabs down so much I would think I should be at or dam close to 40 mph. motor is where I want it, if I can only get the boat to work with.

I'm debating on cutting the old tabs off and putting wider ones on or do some kinda adjustable trim tab not sure yet.