Johnson 9.9 won't run much past idle

[ba_50]

This 1992 Johnson was bought new by the previous owner and used about 3x as a kicker motor. I've put about 20-30 hours on it.

It idles ok but will onl start up on plane, even with 3/4 throttle. At full throttle it gags but keeps going.

The compression is 100# on each cylinder
The diaphragms looked ok in the original pump. I took a fuel pump off an old 18 hp evinrude with a new kit in it and got the same results.

The carburator has a new kit in it and has been cleaned twice.

Both coils are putting out a spark.

The only thing left is timing. I have a light but will need to get a manual on how to do it with this motor.

Does anyone have any other ideas? Thanks. Bob

 

[JB]

Re: Johnson 9.9 won't run much past idle

Every year we see hundreds of "just cleaned" carbs with plugged up orifices, Bob.

When you cleaned the carb did you physically force something through the orifices into the carb throat or did you soak them and blow them out?

 

[ba_50]

Re: Johnson 9.9 won't run much past idle

Every year we see hundreds of "just cleaned" carbs with plugged up orifices, Bob.

When you cleaned the carb did you physically force something through the orifices into the carb throat or did you soak them and blow them out?

JB,

I squirted carb cleaner through a nozzle into all the holes till it came out somewhere else.

This carb was soaked once before all night, but I quit doing that when I found out they are coated with a sealer and that shouldn't be done. Since pushing a wire through the orifaces might damage them I
don't do that either.

Soaking this one probably wouldn't hurt anything now. There could be a stubborn piece of dirt partially blocking the high speed jet.

This one has been cleaned at least 3x.

 

[tashasdaddy]

Re: Johnson 9.9 won't run much past idle

i take some stranded wire, twist 3 or 4 strands together, and clean the orifices, be surprized what get broken free. just because you can see light thur them doesn't mean they are clean. copper wire is softer thant the orifice, so no damage.

 

[ba_50]

Re: Johnson 9.9 won't run much past idle/surge etc.

Re: Johnson 9.9 won't run much past idle/surge etc.

Here's an update:

The roller cam bolt had worked loose and messed up the threads. After tightening, it broke off. So a very loose roller cam was part of the problem.

This carburetor cap was later redesigned with a new needle and other things. These plastic tops apparently warped after warming up causing poor operation.

A mechanic recently told me any plastic tops will warp with heat, so I assume that goes for the redesigned top too.