Set Up Help 11' Tunnel

[moomba]

I have this 11 1/2' Tunnel with center pod splashed from a Liberator that I need some prop help with. I have not run the boat yet. It is all ready for paint and then I need to rig it. The bare hull is around 200 lbs. I have a 4" jack plate going on it. The motor is a 83 60HP Evinrude twin cyl. powerhead Compression is 140lbs. The 15" mid and lower is from a 1987 40HP. It does have power trim and tilt.

I am going to install a nose cone and Low water Pu. so the motor can be run high. Any thoughts as to a transom mounted wtr pickup instead of the coned lower. The gear ratio is 2.42 to 1. It is a premix motor now. My weight is about 175 lbs and the boat will be center steer.I'm not sure what kind of RPM's these motors will turn as I have only run Merc v6's. I have a JSRE 260HP on my STV Euro. Any and all help would be great. Below is photo of motor and the boat when I bought it.

Thanks
Steve

http://i289.photobucket.com/albums/ll213/1moomba/150HP%20and%20Misc%20used%20parts/046.jpg
http://i289.photobucket.com/albums/ll213/1moomba/150HP%20and%20Misc%20used%20parts/sept20200920328.jpg

[MN1]

I can give you some Sport C info. Our 40 hp Tohatsu's have a 13:25 gear ratio and we use Merc Hub Cleaver11.25" to 12" dia x 18" pitch props. No low water pickup and no nose cones. My motor is set at 5/8" above the bottom at 3 degrees trim. Our race weight is 675 lbs.
Hope this helps,
Mark N

[Infoless Racer]

Mark, what would your engine be running at ? 6500rpm? Assume your rev limited is off.

Steve, I am also toying around fitting a 50hp Tohatsu on a Dillon Pro tunnel (11' @ ~220lb). will probably turn a 11-1/2X20 w/o nose cone or low water pick-up, just plugged the upper holes of the water intake and see where that takes me. If I don't get the water pressure thru the engine I will install the low water pick-up instead.

[MN1]

I don't remember what we saw in RPM's. But I think it was around 7300. I heard others were turning 8000 but maybe that was all (SMACK) :)
Mark N

[Infoless Racer]

Wow 7300!! That puts you close to 60mph.....how hard can you run the engine before it disintegrate?? At 7300rpm you are at least 25% above the recommended operating range!

[moomba]

Mark, what would your engine be running at ? 6500rpm? Assume your rev limited is off.

Steve, I am also toying around fitting a 50hp Tohatsu on a Dillon Pro tunnel (11' @ ~220lb). will probably turn a 11-1/2X20 w/o nose cone or low water pick-up, just plugged the upper holes of the water intake and see where that takes me. If I don't get the water pressure thru the engine I will install the low water pick-up instead.

Would you do a LWPU off the transom or do it with a cone??
Thanks
Steve

[Infoless Racer]

Well I am thinking along the lines of off the transom, a simple aluminium water pick-up welded to a bracket and connected to the flushing connector should do the trick. Seen that in the Formula Race hulls.

[JohnsonM50]

Well I am thinking along the lines of off the transom, a simple aluminium water pick-up welded to a bracket and connected to the flushing connector should do the trick. Seen that in the Formula Race hulls.

Ive got some 'go fasts' with both low pick up & transome mount.

http://i35.photobucket.com/albums/d151/mes355/DSCN0363.jpg
http://i35.photobucket.com/albums/d151/mes355/DSCN0241.jpg
http://i35.photobucket.com/albums/d151/mes355/026.jpg
The foot adapt is good because the water shoots up to the pump w/o a hose.
The transome mount does the trick but is more risky & has to be taken loose to remove the motor or tilt it up. The hydro has a good place to drill it in but I had to make the runabout one. Id call the low pickup best because you know its in the water. Running the indicator stream forward to where you can see it from the cockpits a good way to be sure.

[Infoless Racer]

Yeah, absolutely right to have sufficient hose slack to turn and tilt the outboard. A fancy alternative to the tell-tale stream is a cheap water pressure gause. :-)

[JohnsonM50]

Yeah, absolutely right to have sufficient hose slack to turn and tilt the outboard. A fancy alternative to the tell-tale stream is a cheap water pressure gause. :-)

A gauge is good, on the slack note: not too far off center helps;)

[MN1]

Wow 7300!! That puts you close to 60mph.....how hard can you run the engine before it disintegrate?? At 7300rpm you are at least 25% above the recommended operating range!

Actually, we saw 63 mph with the boat setup for competition on the gps.
Also on the transom height, it is the center of the prop shaft that is 5/8" above the bottom with the boat trimmed at 3 degrees. Remember, the farther the motor is setback off the transom the higher it has to go to be the same height in the water when the boat trims. I use AutoCad to find this dimension.
Mark N

[Infoless Racer]

Mark do you have exhaust relief vents on your lower unit? What other mods were done to get the engine howling at the rpm?? thanks

[MN1]

Sport c is a stock class, so no extra holes and stock motor cover. Stock all the way!
Mark N

[JohnsonM50]

[QUOTE=Infoless Racer;85012]Mark do you have exhaust relief vents on your lower unit? What other mods were done to get the engine howling at the rpm?? thanks
The motor will likely turn pretty good Rs no problem stock, :cool:.. if prop, set up & tuning are close or optimal.. pretty fast :D

[Infoless Racer]

noted....this is going to be fun. Will keep my engine stock and see how far i can push the hull. Thanks guys

[JohnsonM50]

[QUOTE=Infoless Racer;85025]noted....this is going to be fun. Will keep my engine stock and see how far i can push the hull. Thanks guys


:cool: Thats what Id do 1st, run what you have & get used to it as you get more from it. Ill bet its an animal accelerating! :D Relief holes may have a negative effect..:confused: but sound cool :rolleyes: [like the Cheery Bomb slogan.. " disturbing the peace since 1976"] :eek:

[moomba]

What RPM's will my 60HP Evinrude twin turn without hurting it??

[MN1]

What RPM's will my 60HP Evinrude twin turn without hurting it??

It should be able to turn 6500 to 7000 with no problem. It is basically the same as a SST 45 powerhead.
Mark N

[moomba]

It should be able to turn 6500 to 7000 with no problem. It is basically the same as a SST 45 powerhead.
Mark N


I need to get a manual for this motor. What should I run the timing at at wide open throttle. I run 25 Deg BTDC advanced on all my v6 Mercs with all the advance boxes in the garbage can. Am I going to need to do any jet changing to run the extra RPM's ??
Thanks
Steve

[MN1]

I don't have an answer on the timing. But Ron Hill or one of the SST 45 racers should know. On the jetting, most motors come from the factory jetted a little rich. Keep it stock for testing props and boat setup. Then adjust if needed later. The SST 45 guys will be your best source for motor tuning.
Mark N

[Infoless Racer]

It should be able to turn 6500 to 7000 with no problem. It is basically the same as a SST 45 powerhead.
Mark N

Mark with my Tohatsu M50D2 3 banger, what rev would it do stock without exploding :D

Guess Sport C runs the Tohatsu 40C which is a small simpler block....

[MN1]

The Tohatsu powerhead used in the D class in Stock Outboard produces 57.8 HP at 6500 RPM. So, I would think 6500 to 7000 should be OK for your motor since it is the same powerhead. I believe this D class motor has it's crank welded by the builder (Bass). But in Sport C I have never heard of any problems with the cranks when turning high RPM's. Crank welding is not permitted in Sport C class.
Mark N

[JohnsonM50]

The Tohatsu powerhead used in the D class in Stock Outboard produces 57.8 HP at 6500 RPM. So, I would think 6500 to 7000 should be OK for your motor since it is the same powerhead. I believe this D class motor has it's crank welded by the builder (Bass). But in Sport C I have never heard of any problems with the cranks when turning high RPM's. Crank welding is not permitted in Sport C class.
Mark N
The stock Tohatsu will be fuel injected While the Bass is carburated? Is there much difference?

[MN1]

The Tohatsu M50D2 is carburated. The new ones produced for consumers are fuel injected and have the model number MD50BE.
So far the only ones I know of being used for racing with fuel injection in the USA will be the Merc 60 four stroke and the motors used in Champ class and drag racing. I'm sure it will work fine. Lots of engineering goes into them.
Mark N

[Infoless Racer]

Guys thanks. That is assuring.

I have a dumb question. I am trying to run the aeromarine research tunnel hull program. I do not have my engine with me yet, it on order. Can anyone tell me the dimensions of the lower unit and skeg. Mark I think you know what I mean as you have the prog.

Torpedo diameter
Skeg width
Skeg height
Skeg thickness

Thanks

[MN1]

I looked at my program and it looks like it is listed in the Nissan category.
If you don't have it I'm sure Jim will find it for you. Shoot an email to him and he will respond with an answer right away.
Mark N

[Infoless Racer]

I just might do that. My program is the 7.0 verson which has very little data on Nissan/Tohatsu, thanks

[marinetech51@earthlink.net]

I can give you some Sport C info. Our 40 hp Tohatsu's have a 13:25 gear ratio and we use Merc Hub Cleaver11.25" to 12" dia x 18" pitch props. No low water pickup and no nose cones. My motor is set at 5/8" above the bottom at 3 degrees trim. Our race weight is 675 lbs.
Hope this helps,
Mark N

Mark, what part of the motor is 5/8" above the bottom?

[MN1]

It's the middle of the prop shaft. But this takes into account the transom setback. So, actually the prop shaft is 5/8" above the water when the boat is trimmed at 3 degrees. (On paper that is).
Mark N

[Infoless Racer]

Mark you have a unique one-off design of your tunnel. You have any pictures posted here in the forum?

[MN1]

Here's some.
Mark N
http://i299.photobucket.com/albums/mm315/MN392/sport20c206.jpg
http://i299.photobucket.com/albums/mm315/MN392/sport20c203.jpg
http://i299.photobucket.com/albums/mm315/MN392/sport20c20rear202.jpg
http://i299.photobucket.com/albums/mm315/MN392/d784.jpg


And now doing some changes to the tunnel shape.
http://i299.photobucket.com/albums/mm315/MN392/SportC.jpg
http://i299.photobucket.com/albums/mm315/MN392/dcp_0869.jpg

[Infoless Racer]

I like your sponson shape. It's different and you are now changing the profile of your aerofoil. I guess to create more lift and move the center of pressure forward .....

Are you tunnel side canted inwards? Are there any benefits do that. Read somewhere it help hold better during turns....

[JohnsonM50]

My Bunky Bowerman hydro has a similar curve where the bottom meets the sponsons forward
http://i35.photobucket.com/albums/d151/mes355/DSCN0213.jpg
Not as radical as the tunnel.

[MN1]

I like your sponson shape. It's different and you are not changing the profile of your aerofoil. I guess to create more lift and move the center of air lift forward .....

Are you tunnel side canted inwards? Are there any benefits do that. Read somewhere it help hold better during turns....


Yes, I am trying to have the lift move forward so I can move weight in the boat forward. The original design was super on the straights but needed a lot of work in the corners and dock starts. There was so much boat out of the water it didn't want to turn. It rides super high, not bow high but the whole boat. Jim's program worked great for such a radical design as my boat. It was just the operator of the program that needed to be more conservative.
When I went to build the boat I did it (exactly) as what the program showed. Even the wing shape. Notice it comes back to about 1/8" at the rear! Tough to do but I wanted to go by the program to the very last detail.
The changes I've made this time are not from Jim's program but from some experience with working on other tunnel boats. It's somewhat based on the design used in SST 60, just smaller. The S bottom is used in many of the small hydros and inboard hydros and in the slower tunnel classes. It's been tried in SST 120 with not so good luck, they go to fast for the design.
The canted tunnel walls have been around for a while. Mine are, in the new design, a C shape. Will it work? Don't know yet, but it will interesting to find out.
Mark N

[Infoless Racer]

My Bunky Bowerman hydro has a similar curve where the bottom meets the sponsons forward
http://i35.photobucket.com/albums/d151/mes355/DSCN0213.jpg
Not as radical as the tunnel.

Yeah, Hall Kelly's 3 point hydro Ben Hur has very similar bottom profile as your hydro. Not as pronounce as Mark's tunnel but similar. Read somewhere this helps lower the pressure differential at the bow and keep it from blow-over while increasing the lift at the aft......:confused:

It did great on the Ben Hur and I am sure too on your Bunky Bowerman.

[Infoless Racer]

My Bunky Bowerman hydro has a similar curve where the bottom meets the sponsons forward
http://i35.photobucket.com/albums/d151/mes355/DSCN0213.jpg
Not as radical as the tunnel.


Yes, I am trying to have the lift move forward so I can move weight in the boat forward. The original design was super on the straights but needed a lot of work in the corners and dock starts. There was so much boat out of the water it didn't want to turn. It rides super high, not bow high but the whole boat. Jim's program worked great for such a radical design as my boat. It was just the operator of the program that needed to be more conservative.
When I went to build the boat I did it (exactly) as what the program showed. Even the wing shape. Notice it comes back to about 1/8" at the rear! Tough to do but I wanted to go by the program to the very last detail.
The changes I've made this time are not from Jim's program but from some experience with working on other tunnel boats. It's somewhat based on the design used in SST 60, just smaller. The S bottom is used in many of the small hydros and inboard hydros and in the slower tunnel classes. It's been tried in SST 120 with not so good luck, they go to fast for the design.
The canted tunnel walls have been around for a while. Mine are, in the new design, a C shape. Will it work? Don't know yet, but it will interesting to find out.
Mark N

Sounds like you are on the right track. Moving more weight forward, shifting the centre of presssure to the bow and with the S bottom, negating the lift a little at the bow. This should give you some control of the directionality in turns. How much weight have you added to the hull thru this re-design?

[JohnsonM50]

Yeah, Hall Kelly's 3 point hydro Ben Hur has very similar bottom profile as your hydro. Not as pronounce as Mark's tunnel but similar. Read somewhere this helps lower the pressure differential at the bow and keep it from blow-over while increasing the lift at the aft......:confused:

It did great on the Ben Hur and I am sure too on your Bunky Bowerman.Ive yet to run it, I read it should ride hi & fast, within its range at least.. not like Marks tunnel tho.:eek:

[quty06]

Mark N,

Nice boat, any dimension eg: tunnel width X long

Thanks in advance
Wfred

[MN1]

Sounds like you are on the right track. Moving more weight forward, shifting the centre of presssure to the bow and with the S bottom, negating the lift a little at the bow. This should give you some control of the directionality in turns. How much weight have you added to the hull thru this re-design?

Well, I added 31" to the length of the tunnel at the front. Sounds like a lot but believe it or not my wing section was only 7 feet long before. It's pretty amazing that Jim's program worked on such a radical design.
So, I put thicker plywood on the tunnel bottom, added the pod, added extensions behind the sponsons (for flotation), cut access holes in the decks for adding weight in the sponsons (we were 75 lbs. light before) and cut the back of the capsule for moving the gas tank forward.
I will take off the aluminum on the transom too. Hard to tell, maybe 15 to 20 lbs. more than before.
Mark N

[MN1]

Mark N,

Nice boat, any dimension eg: tunnel width X long

Thanks in advance
Wfred

I'll be at the shop tomorrow and check again. I don't have that design on the computer anymore. Working on a new one:) The new one is going to be based on F1 designs, deep sponsons and deep pod. And in a kit form. Hopefully it will be ready for next summer or fall. Depends on work schedule.
Mark N

[Infoless Racer]

Mark N,

Nice boat, any dimension eg: tunnel width X long

Thanks in advance
Wfred

Quty, what are you running in Malaysia.....great weather, fantastic food and long rivers there

[moomba]

What happened to my thread asking about props and set ups????????????

[Infoless Racer]

What happened to my thread asking about props and set ups????????????

Got to know what the man runs before we can talk setup mate. Maybe you wanna share with us how the weight distribution of your hull is setup :D?

[quty06]

Quty, what are you running in Malaysia.....great weather, fantastic food and long rivers there

something like this:

[quty06]

at start :

[Infoless Racer]

Quty, nice, are these SST 60 engines? 14 foot tunnel ?? What are the rules you race by? How is your setting for hull??

[quty06]

30-50hp 3cyl yammie, fishing gearfoot, mod to engine is no limit, pump gas, boat length is 10 1/2-12 foot, setting for the hull the highest you can till not lost control.

classed as by number of hp stated by manufacture.

[Infoless Racer]

Quty, what props are the 50hp tunnels running? Any insight about the mods you have done on your rig?

[quty06]

myself, push the boat with Ron prop, most r cleaver & few chopper.

mod is outlaw, but none of them using race fuel.

[Cajun]

In Formula 50, that was the 3 cylinder STOCK tohatsu, we ran at 725 pounds total. I ran a 12" diameter 22 pitch quicksilver cleaver on long courses and a 12" diameter 20 pitch quicksilver cleaver on short courses. Running correctly, the motor would turn the 22 pitch 7200 rpm and the 20 pitch 7400 rpm. Never broke a single motor part, except for spinning crankshafts the first year. We had water intake covers built that would cover the top half of the water intake on the gearcase. I ran the motor in a marathon, 150+ miles running at 1/2 pound water pressure in the straights and bumping 7 pounds in the turns. The course was 4 miles long.
The first video is the old boat running the 22 pitch.
The second video is the second generation boat, 13mph faster than the old boat.
The third video is the old boat on a short course with the 20 pitch:

http://www.youtube.com/watch?v=1efu78GVbYI

The new boat:
http://www.youtube.com/watch?v=BaVKf_yMQuA

http://www.youtube.com/watch?v=9iccZJVfO_I
Danny

[quty06]

that's fast man for stock engine.

[Cajun]

Our rules allowed a nosecone, a 1" hole in each side of the exhaust channel on the lower unit, aftermarket reeds, must have reed stops installed to factory spec, Tohatsu's allowed to tack weld crankshaft, all else stock.
D

[quty06]

no port & head work, yammie is bit sluggish

[Jimboat]

The S bottom is used in many of the small hydros and inboard hydros and in the slower tunnel classes. Mark N

Mark - your new design looks very innovative. i'm glad that the TBDP software has worked so well for you. Your hull is a great looking boat! Good work!

I note you're using an "s-shaped" aerofoil section. Let me know how it is working out for you....very high lift shape, so very efficient....as you know, this shape also shows a somewhat dramatic shift (foreward) in dynamic CG during deceleration, so can require some nifty "driver input" under conditions.

stay in touch, and send pics!

/Jim

[MN1]

Mark - your new design looks very innovative. i'm glad that the TBDP software has worked so well for you. Your hull is a great looking boat! Good work!

I note you're using an "s-shaped" aerofoil section. Let me know how it is working out for you....very high lift shape, so very efficient....as you know, this shape also shows a somewhat dramatic shift (foreward) in dynamic CG during deceleration, so can require some nifty "driver input" under conditions.

stay in touch, and send pics!

/Jim

Jim,
Today was the first test of all of the changes I made to my boat. All went better than expected. We have not lost any RPM's but gained 1 to 2 hundred. The boat is now very close to blowing over but not so fast that it's easy to catch and trim under. The cornering has improved but we need more test time to improve the technique. It's seems like the boat wants to be trimed out in the corners. So, more testing of different driving styles in the corners will be tested next time out.
Here are a few photos from today.
Mark
http://i299.photobucket.com/albums/mm315/MN392/dcp_0996-1.jpg
http://i299.photobucket.com/albums/mm315/MN392/dcp_0998-1.jpg
http://i299.photobucket.com/albums/mm315/MN392/dcp_0995-1.jpg

[Jimboat]

Looks good! is that the tunnel design that we corresponded about recently? The modelling we did showed some good results. Glad that the testing is showing same. Send me some details of your performance observations. Good work, Mark!

[MN1]

Looks good! is that the tunnel design that we corresponded about recently? The modelling we did showed some good results. Glad that the testing is showing same. Send me some details of your performance observations. Good work, Mark!

Well, the last one we taked about was a SST-60 which is planned for this winter. For an un named driver.
It will be an improvent of the exisiting SST-60 designs out now. I need to send some more drawings for you to looks at. But work is still busy here. I hope to in a couple of weeks.
Mark

[Chairman]

Mark,

Will you be bringing your Sport C to Minnesota to race next summer?

[TABARARACING]

Yeah Mark, will you be bringing the boat? Have Sam bring his 60 boat!

For those of you who are not familiar with Mark's and Sam L's project, the boat was extremely fast during the debut. It looked to be keeping up with 45 boats! But with the weight being added to meet the rules the boat seemed to kill the momentum. I hope in time he'll have it iron'd out and most importantly showing up at every C race in the midwest.

The TCPBA (MN boat club) would really like to see the Nelson boat, Kratochwill, and Carl Barrett sport c boats racing again. Those are three very strong teams that all have good equipment.

Regards,

Brian

[OUTBOARDER]

What happened to my thread asking about props and set ups????????????

If it is a stock 40 hp I would suggest 6 part swaps to make it a 50hp.
and 2 more after that to make it equivalent to 45ss = 62 hp.

1. 50/60 hp carbs (1.5" dia throats)
2. 50/60 hp reed cages(stop height was different in some models 50 vs 40).
3. 50/60 hp cyl head smaller dia chamber with less cc's.
3a. mill 50 head for .515 chaber depth = 45ss spec.
note: milling 40hp head IS NOT the same.
4. set timing to 21degs(you can run more but 21 is a good place to start)
5. make a cowbell tuner
6. make sure power pack does not have rev limiter.

1-5 = about 62 hp @ about 6,200 rpms on pump gas

1987 is a good block and hp won't fall off significantly until 7,200 rpms that will put you in
low 50's with stock OMC original 21 p (made for 50twin has extra cup from factory to run engine a litte higher on the transom)

after that see Ron for a prop and he will get you dialed in:cool:

[MN1]

Brian & Bob,
When the test session was over there was talk of coming up to Detroit Lakes, MN with SST-60s and the Sport C and maybe a SST-120.

We still have more testing to do, but the boat seems to be much safer and easier to drive than before.
Mostly because we slowed the power trim down to where you don't have to use super man quick reflexes with your trim finger. Increased cockpit height by lowering the driver and moved steering up and out from around the feet.

Oh yes, set up help. Well, it was turning close to 7500 rpm before Sam let off. Since the motor only had 15 minutes break in time.The motor sat for about about 6 years before being started last weekend. The motor was flat on the transom, about 1/2" lower than what we ran before. The boat now sits very level in the water. No under trim is needed to get on plane now.
Mark

[OUTBOARDER]

If it is a stock 40 hp I would suggest 6 part swaps to make it a 50hp.
and 2 more after that to make it equivalent to 45ss = 62 hp.

1. 50/60 hp carbs (1.5" dia throats)
2. 50/60 hp reed cages(stop height was different in some models 50 vs 40).
3. 50/60 hp cyl head smaller dia chamber with less cc's.
3a. mill 50 head for .515 chaber depth = 45ss spec.
note: milling 40hp head IS NOT the same.
4. set timing to 21degs(you can run more but 21 is a good place to start)
5. make a cowbell tuner
6. make sure power pack does not have rev limiter.

1-5 = about 62 hp @ about 6,200 rpms on pump gas

1987 is a good block and hp won't fall off significantly until 7,200 rpms that will put you in
low 50's with stock OMC original 21 p (made for 50twin has extra cup from factory to run engine a litte higher on the transom)

after that see Ron for a prop and he will get you dialed in:cool:

13x25DAH worked great on V-Bottom with 1986 60hp.
The Scat Cat has Stock 1992 lost foam block and could not swing it.
Does mid 40's with Stock 21P OMC prop & 150lb driver.

Let me know how your testing goes?

[Ron Hill]

Looks like you might have her a little high on the transom!!


ADD;

I NEED TO BORROW THAT PROP FOR AWHILE...