Need some help. I burn a plug every tank of fuel. Using 40% nitro. Very familiar with tunnel and usually won't burn a glow plug. Also, the speed the boat runs is 79 mph. Is this average or slow. It will mill around and take the gas good. Motor is CMB 67 with blue head (if that makes a difference). Set up according to instructions. Any help is appreciated. Thanks
CMD Eagle 67
- Thread starter burger
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shadow
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I would say that you are too lean and or your pipe is too short, and that sounds like pretty decent speed! Try richening up your mixture a little and what length are you running your pipe and also what is the altitude that you are running at.
Cliff
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Prop could be too big too. 79 is a good heat racing speed. My sgx 67 mac runs 78 to 82 in heat racing form depending on the air density and other things that affect performance.
I made an error. It's a MAC 67 motor and the pipe length and prop are what Andy Brown reccomended. Running at sea level. When I richen the motor I can only get in the mid 60s, but it still burns plugs every tank. Thanks for the help.
Duck899
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What pipe? Is the engine stock? Stinger internal diameter?
ALLAN YUEN
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How old for MAC67? did you check on measure for head shim? and check on smooth or rough on bearings (front & rear)?
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Maybe not enough head shim. I would guess you are using a high quality plug. McCoy Mc-9's or Rossi #7's are my favorites and the only plugs that will last in my CMB 101.
79 M.P.H. is movin'. The setup must be close other than the glow plug thing. I tried some crappy Dynamite Mc- 9's and they were doing same thing as yours.
Thanks Daniel
79 M.P.H. is movin'. The setup must be close other than the glow plug thing. I tried some crappy Dynamite Mc- 9's and they were doing same thing as yours.
Thanks Daniel
mark voorhies
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burger,
if your runnin 79 on 40% your doin good with pipe and prop. I don't think you have a CMB,
probobly a MAC, take a closer look at bearings! They are takin plug out.
Thanks for the reply. I thought the boat should run in the high 80s since my 21 tunnel runs high 50s. Thanks, I'll keep working on the plug problem.
It is a MAC, must have had a brain fart. Thanks
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