1985 Grand Sport 3400 losing power on starboard engine .

[Jersey Joe]

I had the same problem last July with the starboard engine on my 88' Gran Sport. It ran fine up to 2,000-2,500 rpm, then would die above 2,500. when I throttled down again it ran fine. It turns out it was a leaking diaphram in the stbd mechanical fuel pump. You can check it by looking at the clear overflow hose that runs from the fuel pump upto the carburetor. It should be empty. Mine wasn't, it was full of gasoline from the leaking bad diaphram. See photo. That could explain the fuel smell too. In addition, it's a good habit the change the engine oil at the same time because it could be contaminated with gasoline that leaked into the bottom of the block/pan. Runs perfect the last two seasons.

fuel pump.PNG

[Grand Sport Guy]

I have a feeling the float may have been sticking. I ran a can of seafoam through it and after running it for a day I came back to the boat the next weekend and boat ran great. I've been running it for over a month now with no issue. A couple other issues popped up. Thermostat stuck, raw water impeller/pump. But I can't complain, the boat sat for 2 years in dry dock.

[goodday]

Sounds like you got the gremlins figured out, so many issues arise when things set for awhile and just purchase , enjoy