Reply To: 1983 70 HP Johnson poor running

[Don]

OK, you had the bowls off, but did you remove and clean the high speed jets that are in the bowls behind the hex drain plugs?
Find something that can pinch off the hoses to the carb primer nipples. If you can’t find something to clamp off the hoses, simply remove and plug them two at a time…
Now try the primer again at high speeds where the engine falters. Repeat this until you have tried each cylinder on its own. Hitting the primer with all three hoses connected might have confused the issue a bit.
RPM should drop if the cylinder is firing correctly
RPM will pick up if there is a fuel supply/carb problem with the cylinder
RPM will stay the same if the cylinder isn’t firing, which doesn’t seem to be your issue
One final point. Sometimes those brass primer nipples of the carbs get plugged up with will confuse the issue because there will be no RPM drop/increase on a cylinder with a plugged nipple…
So, try pushing the primer at slower speeds when the engine is running OK (one cylinder at a time), the RPM should drop down because you are flooding the cylinder. Clean out the brass nipple if RPM doesn’t drop at lower RPMs.
I know we have discussed this before, but perhaps there is a fuel supply issue to the carbs…I think you have already had the filter cap off. Have you tried a separate 6 gallon tank and hose (make sure it is premixed 50:1). Have an assistant pump the primer bulb while the engine is misbehaving also…