Need some help

[FreightTrain]

Ok guys I just bought a boat with a 1992 yamaha 55hp motor on it. When I took the boat out for a test run it ran fine for about 10 mins. Then after several stops and starts it began to have a slight miss at wot. I kept going for another 5mins or so and then the motor started acting like something was holding it back and the power and rpms dropped off quite a bit. <br /><br />During this time the motor would run fine for a sec and then go back to running like crap over and over again. The previous owner claims he had the carbs rebuilt about a year and a half ago and he thought it was carb related and they needed to be cleaned. I checked the compression on the motor and it was 140lbs on both cyl. <br /><br />On a side note when I went to losen the spark plugs the top plug wasnt any tighter then hand tight and both plugs looked pretty oily. Ive went ahead and bought new plugs but havent installed them. Does anyone else have an idea what could be causing this hesitation problem. The motor fires up first try every time and runs smooth just at times it feels like someone forgot to pull up the anchor. And yes I made sure the anchor was up lol.

 

[rodbolt]

Re: Need some help

sounds like it could be fuel related, may be time to clean the carbs and replace the fuel pump. also look for any restrictions using a vacum gauge teed in the fuel line. vacum should not exceed 4"Hg at the pump intake. could also be a spark issue, that may be a bit tougher to find at or near WOT.<br /> when was the last test of the alarm system done and the last cooling system tune up?

 

[FreightTrain]

Re: Need some help

I just bought the boat last week and everything the owner said he had done I took with a grain of salt cause you really cant prove it unless there are receipts. Like I said he claimed he had the carbs rebuilt but it wouldn't suprise me if they needed it again also.

 

[rodbolt]

Re: Need some help

you can rebuild them before lunch and if you get trash in them during lunch your gonna have to do it again after lunch, same as compression. you can have good compression in the AM and a blown powerhead from dirty carbs in the afternoon. fuel pump diaphrams go bad as well.<br /> impellers go bad when sitting,