68 Evinrude 9.5hp idles ok but sputters at high speed.

[cudajim]

This outboard fired right up, has good compression on both cylinders, good spark too. It idles just fine but sputters at high speed. If I put my finger over the carb it (choke it a bit) and it runs really well. I took the carb apart, it was really clean everywhere but I cleaned it anyway and put it all back together with no change. I also set the points to exactly .020. One was a tiny bit off, the other right on. It ran very slightly better but still not good at high speed. I have 2 of these motors both doing the same thing, can't figure it out.

 

[Crosbyman]

were the HS jet orifice inspected, cleaned out, air blown ? they sit way at the back of the bolt at the bottom of the carb below the LS jet needle/cable

it seems to be starving and choking the carb helps it to suck gas from the HS section of the carb

tried pumping the bulb when it starves at HS ….? if it helps maybe the fuel pump is so so

tank vent open ?

 

[kbait]

Is it breathing it’s own exhaust? Lake test with cowl off to test. If it tests great at max throttle, that’s the issue. Report back!

 

[cudajim]

I am running it with the cowl off so I doubt it's breathing exhaust. Also, on this model there is only one jet adjustment which is totally clean. I also tried to pump the bulb with no effect at all.

 

[racerone]

No---- there is a fixed high speed jet ( orifice plug ) in the very bottom of the carburetor.-----It MUST be clean----And look at sparkplug wires where it comes out of the magplate.----Worked on one recently where wire was arcing out to ground.-----=A magneto analyzer can be used to sort out that wonderful magneto.------Or start with running it with a timing light at full throttle to see if you have spark issues or not !!-----Simple trouble shooting is the path forward.----And 2 motors is not many as I have about 10 of them to rebuild / check out , or for parts !

 

[Crosbyman]

if the ignition is OK, and not inhaling fumes ………. it is not sucking gas reread post #2 find and clean the High speed jet behind that bolt !

 

[Crosbyman]

so… how did this story end ….