frusterating mercury

[broken_line]

so i just recently bought a boat with a merc, clasic 50 45 hp motor.. and whenever i run it wide open it will eventually cut back to about 3000 rpms and go no higher and run rough, if i fiddle with the warm up lever and re start it, sometimes after that its fine. its really beginning to be a saftey issue as i fish the river ALOT. im at a loss.. ive tried new plugs, sea foam and everythinh else you go to look at when something doesnt run right.. what could this be?

[boatfixer]

Fuel pump or dirty filter. Have you tried pushing in the key while its cutting back? The extra shot of gas can tell you whether or not its fuel related.

[broken_line]

yeah i do that and it dies all together.. it must be a spark issue then?

[BoxMN]

Are you SURE the tank vent is open all the way, and not rattling shut?

[boatfixer]

yeah i do that and it dies all together.. it must be a spark issue then?

Easy way to find out is the timing light idea I often suggest. Hook up a timing light and take her out. Watch the light, listen and see if you loose spark when this happens. You may have to try each cylinder. The stators on those have a low speed and a high speed winding so its possible the high speed is faultering. If nothing else, you will start to eliminate things that could be wrong.

[broken_line]

i did the timing light and it was off a hair, but not the problem.. so i narrowed it down to the bottom carb was clogged, i filled the fuel filter with a little oil, topped it off with starting fluid and carb cleaner put the fuel line back on.. and it runs fine now! still starts a little rough but top end is great! `

[shortfatguy]

if the carb was dirty you should take it apart and clean it. No other method is going to ensure that you dont have dirt in it or clogged jets. Clogged jets = burned down engine. Not a good thing.