11 MOD Tunnels - Caines Racing

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Jarcaines

Well-Known Member
Supporting Member
Joined
Jul 14, 2008
Messages
421
Joey and I ordered a couple .67 outboards and LeeCraft XT460s from Ron at NovaRossi. Starting to layout the plan for putting them together.

Well try and keep this updated with the progress. Let us know if you have any large outboard or LeeCraft set up advice.

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After changing from a K&B to the Nova, had to add more weight to keep the nose down. It wasn't because differences in motor weight, it was the added power the Nova has over the K&B. Didn't check the CG afterwards.
 
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Both my XT 460’s were epoxy glass hulls with no gel coat. They were very light hulls and i had to add a lot of ballast weight to keep them on the water powered by a 45 Rossi River King. Very fast boats that taught me a lot about lift vs mass and driving finesse. It should be interesting to see how the gel coat fiberglass version of the hull handles as much power as that 67 Nova should be able to put out. There was a lady in D4 that was dominant in D tunnel with her Nelson powered XT 460. She had that boat dialed, and she could drive!
 
JR,

Remember the starboard sponson on a Leecraft is about 1/8 deeper than the port sponson. Square the motor mount with the top of the transom and not the setup board for this reason. Use the Prather/Mecoa mount as this is the mount Tommy desiged the transom inset to use. I would start with the midline of the prop shaft bullet even with the bottom of the sponsons. Leecrafts love a little tuck on the engine before you set the prop height. You can fine tune this at the race site so take your setup board. Start with CG around 9.5 with weight in front of the radio box. Also place weight on the floor of the tunnel right on the CG point after you finish the above. Start with about 6oz. Extend/blend the pad/rocker forward to about 6. Focus more on the forward end of the pads as we want to keep the nose down. Cross hatch the sponsons with a pencil so you can monitor where you are removing gelcoat. This is critical. Dont be surprised if you just start to see the gelcoat start to thin out or disappear on the front end of the pads. Use a high quality T sanding bar thats at least 12 long as this pad must be perfectly flat. Use that same bar to run inside the sponsons to make the lowest edges of the sponsons very sharp. Also hit the flat side of the rear of each of the sponsons to make the trailing edge of the sponsons sharp as well. I use stick-on Napa wheel weights inside the tips of the sponsons to trim for water conditions. Start with a lynx cut 1455 or 1457. Play around with tip cup to reduce bow lift and gain stern lift. The latest props from ABC are killer props but will require some testing as the rake on these props will really help reduce the bow lift. Hold on, you are in for a ride!!! You or Joey can call me anytime if you need my help.
 
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Thanks a ton guys! Great info.

I have noticed that everyone runs their tunnel fuel tanks in the very back of the boat. Is there any reason they dont center them on the CG like a scale or sport hydro? Seems like putting the thing that changes weight as you drive at the CG would have the least effect on the handling of the boat during the course of a race. Just some things I am thinking about with it.
 
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Thanks a ton guys! Great info.

I have noticed that everyone runs their tunnel fuel tanks in the very back of the boat. Is there any reason they dont center them on the CG like a scale or sport hydro? Seems like putting the thing that changes weight as you drive at the CG would have the least effect on the handling of the boat during the course of a race. Just some things I am thinking about with it.
JR, some guys center the tanks on the CG so it doesnt change during the race. The only reason I dont is due to the platform is already there for the tanks on a Leecraft and the install easier as the tanks are not in the way of the push rods exit on the rear of the radio box.
 
Both my XT 460’s were epoxy glass hulls with no gel coat. They were very light hulls and i had to add a lot of ballast weight to keep them on the water powered by a 45 Rossi River King. Very fast boats that taught me a lot about lift vs mass and driving finesse. It should be interesting to see how the gel coat fiberglass version of the hull handles as much power as that 67 Nova should be able to put out. There was a lady in D4 that was dominant in D tunnel with her Nelson powered XT 460. She had that boat dialed, and she could drive!
That lady would have been Mrs Cathy Pruesse....very fast and stable 460... Raced against her a few times....
 
Both my XT 460’s were epoxy glass hulls with no gel coat. They were very light hulls and i had to add a lot of ballast weight to keep them on the water powered by a 45 Rossi River King. Very fast boats that taught me a lot about lift vs mass and driving finesse. It should be interesting to see how the gel coat fiberglass version of the hull handles as much power as that 67 Nova should be able to put out. There was a lady in D4 that was dominant in D tunnel with her Nelson powered XT 460. She had that boat dialed, and she could drive!
That lady would have been Mrs Cathy Pruesse....very fast and stable 460... Raced against her a few times....
Cathy with her XT-460.

Lohring Miller

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Cathy with Leecraft.jpg
Yes indeed, Cathy Preusse is who I was referring to... and she is entered in the Nitro Nationals.
 
Jarcaines,

I would like to apologize to you for stepping on your thread. Your boat should be ballistic with that 67 nova. Please keep us posted with your progress.
 
Thanks a ton guys! Great info.

I have noticed that everyone runs their tunnel fuel tanks in the very back of the boat. Is there any reason they dont center them on the CG like a scale or sport hydro? Seems like putting the thing that changes weight as you drive at the CG would have the least effect on the handling of the boat during the course of a race. Just some things I am thinking about with it.
JR, some guys center the tanks on the CG so it doesnt change during the race. The only reason I dont is due to the platform is already there for the tanks on a Leecraft and the install easier as the tanks are not in the way of the push rods exit on the rear of the radio box.
Ron,

Yeah, that makes a lot of sense. I think since we are making our own radio boxes, I might play around with where things are positioned a bit. If I cut into the fuel tank platform, is there flotation in the hull? Do you think it will weaken the structure much? I am thinking of just cutting some of the front portion of the platform out and getting the fuel tank down in the hull a bit right at the CG. Also curious about pressure for the fuel system. I know part of why the tanks were high up on that platform is for fuel flow. Does the NR with the tune pipe create a lot more pressure for the fuel system then the old K&B stock exhaust? I would assume so, but I am just guessing on these things.
 
Thanks a ton guys! Great info.

I have noticed that everyone runs their tunnel fuel tanks in the very back of the boat. Is there any reason they dont center them on the CG like a scale or sport hydro? Seems like putting the thing that changes weight as you drive at the CG would have the least effect on the handling of the boat during the course of a race. Just some things I am thinking about with it.
JR, some guys center the tanks on the CG so it doesnt change during the race. The only reason I dont is due to the platform is already there for the tanks on a Leecraft and the install easier as the tanks are not in the way of the push rods exit on the rear of the radio box.
Ron,

Yeah, that makes a lot of sense. I think since we are making our own radio boxes, I might play around with where things are positioned a bit. If I cut into the fuel tank platform, is there flotation in the hull? Do you think it will weaken the structure much? I am thinking of just cutting some of the front portion of the platform out and getting the fuel tank down in the hull a bit right at the CG. Also curious about pressure for the fuel system. I know part of why the tanks were high up on that platform is for fuel flow. Does the NR with the tune pipe create a lot more pressure for the fuel system then the old K&B stock exhaust? I would assume so, but I am just guessing on these things.

JR,

Either way the tank needs to be up high due to the inherent fuel feed problems with outboards because of the height of the carb. We add a hopper on top of the main tank to reduce air bubbles and to get the fuel feed closer to the level of the carb. Personally, I would not cut out that area of the tunnel. The FE guys get by with it as they insert a full length radio box and attach to the sides of the top deck and bottom of the radio box to the lower half of the hull and this re-establishes the structural integrity of the hull. Cutting out that area for a tank to clear would weaken the hull strength considerably.
 
Thanks a ton guys! Great info.

I have noticed that everyone runs their tunnel fuel tanks in the very back of the boat. Is there any reason they dont center them on the CG like a scale or sport hydro? Seems like putting the thing that changes weight as you drive at the CG would have the least effect on the handling of the boat during the course of a race. Just some things I am thinking about with it.
JR, some guys center the tanks on the CG so it doesnt change during the race. The only reason I dont is due to the platform is already there for the tanks on a Leecraft and the install easier as the tanks are not in the way of the push rods exit on the rear of the radio box.
Ron,

Yeah, that makes a lot of sense. I think since we are making our own radio boxes, I might play around with where things are positioned a bit. If I cut into the fuel tank platform, is there flotation in the hull? Do you think it will weaken the structure much? I am thinking of just cutting some of the front portion of the platform out and getting the fuel tank down in the hull a bit right at the CG. Also curious about pressure for the fuel system. I know part of why the tanks were high up on that platform is for fuel flow. Does the NR with the tune pipe create a lot more pressure for the fuel system then the old K&B stock exhaust? I would assume so, but I am just guessing on these things.

JR,

Either way the tank needs to be up high due to the inherent fuel feed problems with outboards because of the height of the carb. We add a hopper on top of the main tank to reduce air bubbles and to get the fuel feed closer to the level of the carb. Personally, I would not cut out that area of the tunnel. The FE guys get by with it as they insert a full length radio box and attach to the sides of the top deck and bottom of the radio box to the lower half of the hull and this re-establishes the structural integrity of the hull. Cutting out that area for a tank to clear would weaken the hull strength considerably.
Okay, thanks Ron. Guess I'll scrap that plan.
 
JR,

I have 12 oz and 16 oz fuel tanks that I won't ever use. You and Joe are welcome to them. I can bring thing to the practice day on Saturday.

JD
Jerry,

Sounds great! Thanks man.

When we convince you to build a .67 mod, I can give them back...
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Been there(K&B 67 Outboards both stock and mod), done that, have decided that downsizing to 21 OBs works well. But, it will be interesting to see how the new NV 67 OB performs. At least with a tune pipe it will not be as loud as the stock K&B 67 OBs. That engine was the ultimate "Fuel to Noise Converter."

JD
 
JR,

I have 12 oz and 16 oz fuel tanks that I won't ever use. You and Joe are welcome to them. I can bring thing to the practice day on Saturday.

JD
Jerry,

Sounds great! Thanks man.

When we convince you to build a .67 mod, I can give them back...
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Been there(K&B 67 Outboards both stock and mod), done that, have decided that downsizing to 21 OBs works well. But, it will be interesting to see how the new NV 67 OB performs. At least with a tune pipe it will not be as loud as the stock K&B 67 OBs. That engine was the ultimate "Fuel to Noise Converter."

JD
Jerry,

Remember my dad's 67 Mod that he ran without the pipe? He just hacked off the back of the constricted part of the lower end exhaust outlet. That thing was SO LOUD. Eventually you made him muffle it, so he took a can muffler, cut a rectangle hole in it and mounted it sideways on the back of the lower end similar to how the new 7.5 K&Bs are muffled, but before that was available. Then he drilled 4 or 5 holes in the bottom of the muffler so that it wouldn't actually do anything...
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You can sort of see it here:

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