stumble and rough running 1999 Outback

Boat recently started to lose power at 36 mph and has had trouble maintaining speed after 34 mph. My driver said it was surging a bit especially in the corners.

I do a one mile up the lake at 36 and then a left hand keyhole turn and come right back down the same path. He said it was struggling to maintain speed and then surged in speed on the turn. I ski a lot, and one of my buddies on shore who also drives for me said the boat sounded different coming down the lake.

I checked the carb filters, the fuel pump flow, the fuel water separator, sprayed carb cleaner around the gaskets for air leaks, checked the plugs, distributor and cap look fine, advanced and retarded the timing, (runs a little better retarded) checked the strainer and impeller for cold circulation, also checked water pick up. Warm water is flowing out of exhaust, both sides. idle is a bit rough and it just sounds off. Going down the lake it usually sounds smooth and jumps from 36 to 40 very quickly. When I tried it today after all that checking it did not respond well. Am I missing something?

check the carb.

Rebuilt 2 years ago and was running great until the surges and stumbling. This was an intermittent problem as well. It did it a few times and ran perfectly a few times. Now it seems stuck on stumble at above 3800 rpms but just does not sound or feel like it used to getting there. Revs fine, under load is the issue. What should I check on the carb? Primary and secondary flow?

I twice had to replace the electronic ignition seperated by 10 years. Same issues.

Retarded the timing a bit and skied at 34. Boat was not running well according to the driver and it took off in the turn again and accelerated like it should. Does this mean the float is stuck or needs adjusting? I can hear that it is off at idle and slow speeds, and a little more pronounced at 34 to 36. Above that it really struggles.

So get a new distributor, a cap and rotor assembly, new plug lines, etc? New plugs will be here in a few days. Is it damaging the engine to have it retarded and running poorly? Thanks

What engine do you have? What carburetor?


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350 chevy indmar Holley 680 changed the cap and rotor, no difference

If it is similar to my 98 with a 350 PCM, the carburetor has a Moomba number to it and a rebuild kit by Holley requires a different a different power valve than comes with it. That has messed up some boats.

Found that out a few years ago. Changed the power valve after a rebuild of the carb and it ran much stronger. Thanks

Boat revs to 3500 and sounds great. As soon as I engage the trans it is off. Anyone change to a electronic ignition distributor? I can get the whole thing, but I am not sure how to set it up or get the old one out.

Ran a lot better after putting a new fuel water separator in. Replacing the raw water pump today for a substantial leak under load.

Replaced the fuel pump and it is still running a bit off. Just does not sound the same. Idle is good. Took the carb off and checked the float bowls, clean and no debris.

I will ski behind it and see if it still has issues under heavy load, and not just normal load. It only seems to falter when I ski, not just cruising around.