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1980 7.5 HP Johnson carb issue

H

helgymatt

New member
1980 7.5 Johnson - model number J8RCSS

The carb was serviced last year by mechanic. Unknown what parts replaced or problems encountered. Originally the engine would only run for short time with choke on. After service idle and low speed performance improved, but top speed performance very poor. Boggs down and will not reach top seed. Pumping fuel ball doesn't improve performance telling me this isn't a fuel pump issue. Correct?

Followed up carb service with new fuel tank lines. New fuel. Fuel filter screen on pump clean. Have not replaced plugs. Has champion L86C installed instead of preferred L77J4 as noted on tag on spark plug cable.

I recently pulled the carb myself. Found the damage evident in attached photo on the high speed jet/port. It looks like someone marred it up with a screwdriver. The large tube is damaged and partly gone at about 1/6" depth much of the way around the circumference of the tube. I don't see that this part is replaceable. Can a shop fix this or can someone help point to replacement carb assembly? And is this likely the culprit? I did once notice improved performance right off the boat ramp for 200 yards, then poor again. Maybe the bowl had more fuel than normal? Or could this be a spark plug, thermostat, fuel pump, compression, water pump issue?

carb.jpeg
 
I have 1981 Johnson 7.5. Running real erratic. Particularly on the water. It will be fine, then start to lose power and die. Hard to restart. I’m running fresh Trufuel. Spark plugs are clean. Just tore down the carb and it was clean but the high flow jet looked just like the one in the photo.
 
Start with a compression test.----Post the actual values here.------Water pump impeller replaced every 5 years or so ?----Also test run with another tank and hose.-----In the above picture that is NOT the high speed jet.
 
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