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K&B sport 40 advice needed.

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K&B sport 40 advice needed.

Old 09-07-2007, 11:24 AM
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Dom G
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Default K&B sport 40 advice needed.

Hi guys.
I bought a sport 40 eleven yrs ago , right after that I got posted away from my club and friends ( in the military) Now that I'm back I finally built a 7.5 Hawk outrigger for it . Now for my Question: Does anyone know how long the tune pipe should be to get max performance out of the motor? I'm running at sea level with a prather tune pipe and a prather 240 prop on 25% nitro. Any direction would be greatly appreciated as I'm used to running outboards and new to inboard tuning. Thanks Dom.


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Old 09-07-2007, 03:34 PM
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gooycheese
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Default RE: K&B sport 40 advice needed.

I have a 7.5 hawk build thread here on rcu, I was told that 9 3/4 -10 would be a good place to start. Your pipe in the pics looks way long? I also had to add shims under me rear boom mount to lessen the angle of attack, in the kit i got there was 4 white peices of plastic (I have all 4 under the rear boom and will add more still. It almost looks like your turn fin is mounted on the outside of the spar, if it is i would move it to the inside of the spar also (never seen one mounted on the outside like that). To measure pipe length measure from center of glow plug following the center line of the exhaust to the fat of the pipe. It would be great to see some more pics of your rigger out of the water too


Paul

What Prop are you running? I am running a 1457 with an OPS .45 engine
Old 09-07-2007, 07:24 PM
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Dom G
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Default RE: K&B sport 40 advice needed.

Thanks for all the info . I'll try it all!
I set up the boat just like the pics that came with the plans.
My prop is a prather 240 that I bought 11yrs ago when I bought the motor.
I'll post some more pics later when she's running better. Have patience as I only have @#$%^$#@ dial-up!

Your Boat looks awsome. I want one of those cowls that you have!

Take it easy. Dom
Old 09-07-2007, 11:04 PM
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gooycheese
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Default RE: K&B sport 40 advice needed.

For a cowl goto www.cdrace1.com it probably wont be listed but there is contact info there, David Preusse will hook you up. I will say based on what you just said your rear angle of attack is too much, i had mine set like that and it was too much had to lower the front of the rear sponsons down about 1/4 to 3/8" there is alot of setup involved in getting this boat to ride right. I still don't have mine running as nicely as I would like it. It would sorta hop and I changed setup and was better but still need to change some more so the boat rides smooth and tight to the water, no hopping.


Paul

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