1970 Johnson 9.5 model 9R-70C

mek07c

Cadet
Joined
Sep 5, 2008
Messages
26
I just rebuilt the carburetor on a Johnson 9.5 motor and it runs great while in neutral gear. When I put it into forward gear, it runs fine at low speed but when I get at higher speed the motor seems to bogg down considerably. When it does this I can stop and put it into neutral and rev it up and it doesn't bog down. Twice I have had the boat planed out and running pretty fast for a few minutes but most times it just bogs down. I have no idea what could be causing this. Any suggestions? When I rebuilt carburetor I cleaned out entire thing including the high-speed jet and replaced float. I already bought brand new gas tank and fuel line hose and cleaned fuel filter. Please help!
 
D

DJ

Guest
Re: 1970 Johnson 9.5 model 9R-70C

Does it bog down if you run it with the hood off?
 
D

DJ

Guest
Re: 1970 Johnson 9.5 model 9R-70C

Good. That eliminates an exhaust leak.

You are losing a cylinder. For what reason, we have to figure out.

Can you get your hands on an inductive type timing light? If so, put the inductive lead on one plug wire and then the next. See if you are losing spark on one cylinder.
 
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