Mercruiser 220hp no top end

It is a 5.0 V8 alpha 1 drive

Thank you all for the feedback, i will try chainging the water seperator, I do not have an aluminum tank so hopefully there is no corrosion problem.

UPDATE----- i changed the water seperator last night and the engine ran smoother for a while but then the problem came back, not as severe as before but the engine will still drop RPM's when at higher revs. I was wondering if anyone has had any luck with the Ethanol fuel additives i have seen advertised. Thanks for any input.

I did not check (could not find) the filter on the engine, but when i pulled the old seperator off i did see a good amount of Phase seperation....is it possible i only have a seperator and no filter?

I saw a mix of water, cloudy fuel, and some sediment on the surface.

BTW, my last two fuel ups have been at a reputable marina in Port Jefferson Harbor, and a Hess gas station on land.

There sometimes is slight shaking, but it feels like shaking from the engine running rough because it is not getting enough fuel.

The problem went away for about 10-15 min, which is why i plan on putting the startron in the tank, run for a little while with the existing seperator at low speeds when the engine runs fine, then change the seperator and see where that gets me.

UPDATE---- this past weekend went out on saturday, dumped startron in the tank. Did not seem to have any problems, i ran the boat very lightly, did not push it. Ran no higher than 3400 rpm, just enought to get her on plane. I now have 2 extra water seperators that i will swap one out after a few more runs... thanks to everyone for the helpful input.