evinrude 9.5, i`m kinda stumped

[ultra353]

I`m looking for suggestions where i should look next for my 1/4-midrange running problem. It starts up great, idles well and has good top-end, but about 1/4-throttle up to about 3/4 it seems to act like its running rich or dieseling. It goes from running smooth to a little rough then back to smooth and so on, top end it runs smooth. The top cyl seems to be the one giving me the problems as the plug is dark(not wet) and the lower is tan, switching plugs have the same results.
It has new points(set at .020 checked several times and cleaned with contact cleaner) condensers, coils, wires, plugs and jumps a 3/8 gap with a blue spark. Carb has cleaned and carb kit installed, float set correctly, rebuilt fuel pump, new head gasket, exh gaskets. While its was running i sprayed wd-40 over all seals and gasket/mating surfaces looking for air leaks -no change in rpm. Shift rod seal, water pump seal and exh clam shell seal all good. Compression was at an even 75lbs, reeds looked to sitting flush with no visiable light seen. Any ideas?

 

[Daviet]

Re: evinrude 9.5, i`m kinda stumped

What is the model# of the engine, it helps to know what we are working on.

 

[ultra353]

Re: evinrude 9.5, i`m kinda stumped

It`s a `68 evinrude 9.5 sportwin

 

[Fuzzytbay]

Re: evinrude 9.5, i`m kinda stumped

That model has a fixed jet, If memory serves me correct. I had a similar issue on a 64 20hp, turned out there was a buildup around the three holes on the side of the fixed jet making the jet size a bit smaller than it is suposed to be. So in the midranges it didn't perform right, but run up to top end it sounded good. I cleaned out the three holes in the jet with a tip cleaner for cutting torches, and that fixed the problem.

 

[ultra353]

Re: evinrude 9.5, i`m kinda stumped

Everything in the carb is spotless. Could the fuel pump be leaking even though it was just rebuilt and works fine?

 

[Daviet]

Re: evinrude 9.5, i`m kinda stumped

When you cleaned the carb, did you remove the core plugs and clean ALL of the passages?

 

[ultra353]

Re: evinrude 9.5, i`m kinda stumped

Yes all core plugs were remove and passages were cleaned when the carb was rebuilt.

 

[steelespike]

Re: evinrude 9.5, i`m kinda stumped

From your description It sounds like the top cylinder has the problem.
Be sure The coil wires are inserted in the coils right.be sure the stator plate is stable, doesn't wobble.Coils mounted to the bosses on the plate.
Swap the coils perhaps one is defective.Are the wires new solid core?
Is the stator cam picking up the throttle lever at the right point?
Sometimes there is a ground wire on the stator plate.