1999 50hp bigfoot low power

[joeneal1986]

i have a pontoon boat that i just bought off my uncle with a 1999 50hp bigfoot merc on it. the problem i am having with it is when its in gear it has little or no power rpms only get up around 3500, i checked and cleaned the carbs out everything from what i can tell looks good but what i did notice the other day is when me and my uncle had it out you can cover some of the opening to the carbs (almost like chokeing it down) and only allow a portion of the air in that it was designed for and it runs fine some where its running lean im not real familer with these motors so any help on maybe riching up the carbs or do they need a rebuild etc. thanks

 

[Silvertip]

Re: 1999 50hp bigfoot low power

you should pull the spark plugs and read them. Yes -- they tell a story. A cylinder firing normally will have a light tan/brownish color. A lean running engine or one that has had water passing through it will be white and one that is not firing will likely be wet, blackish due to fuel/oil that is not being burned. Make sure there is spark on dead cylinders. Rebuild carbs on cylinders that appear to be lean. Of course no engine can make full power if the carb throttle plates are not opening fully, timing is not advancing properly or if the engine is simply tired (as in worn out). Compression and/or leakdown tests will provide a relative indication of engine health.