Re: 1978 Johnson 75 hp Stinger stalls when throttled up

[Don]

Yeah, I wouldn’t attempt to remove the jets without having the proper tool, that is probably how one of the jets got damaged. In any event, did you remove the jets? If not, I would just use a little cloth pipe cleaner to clean the jets while they are still installed in the carbs. Simply drain the carbs, now spray engine tuner/carb cleaner on the pipe cleaner and run it into the bowl drains and through the high speed jets. Once removed from the jets, a brown/green staining on the pipe cleaner indicates dirty jets. Before reinstalling the carb drain plugs, reconnect the fuel line and pump fuel through the carb bowls in an attempt to wash out any debris dislodged while cleaning the jets. Yes, not the most effective way of cleaning up the carbs, but this might solve the problem for now. Keep in mind that jets that are loose in the bowls can create a fuel restriction as well.
Perhaps the fuel pump is weak, or there is an air leak/restriction in the fuel system causing the engine to starve at high speeds.
Have an assistant pump the fuel bulb constantly while you accelerate the engine to see if that helps. Any signs of water in the fuel?
Be sure to heed everyone’s advice about propping this engine, it is really meant for a light/high speed hull, and has little mid range power for pulling skiiers or planning difficult hulls.
But, it seems like I have jumped ahead as well. Listen to Frank, the sync/linkage specs have to be right or the engine will stumble/stall when accelerated.