Engine losing power?

[dtwallace84]

When running my 140hp mercruiser for around five minutes at 4500rpm it will suddenly drop off to around 3700rpm and starts backfiring and running poorly, and its noticable in the power and speed of the boat when it drops off. I winterized the boat myself and dewinterized it myself (first time ever doing both). My gas tank was around 15gallons empty when winterizing and was not filled back up until the other day. I put some seafoam in it and topped it off, but can that much condensate build up to where it will run crappy after a few minutes. I changed my filter as well, and did a full tune up on the engine before running it. Does anyone think something else could be wrong for example the timing or anything?

Thanks for any replys,
dtwallace84

 

[Don S]

Re: Engine losing power?

Do a compression test and check your carb for water. Unless you have a water seperating fuel filter (which you should have) there is no way of telling if you have water in the carb without taking the top off. (new gasket required)
An empty fuel tank is a condensation magnet. Depending on your area of the country, it could be nothing or a gallon.