PLEASE Help! Mercruiser problems above 4000 RPM

[Wyomingman]

I had my 2002 Mercrusier 4.3 MPI, serial number OM322808, Alpha One out for the first time over the weekend. The boat started fine, idled fine, excelerated good and ran smooth up until 4000 RPM. Once above 4000 RPM the motor would surge up and down in RPM's jerking the boat forward and back until I throttled down below 4000 and then it ran smooth. I ran it all day long below 4000 RPM's with no problems. Any ideas what is causing this? would like to get it fixed before the holiday weekend in 4 days but the shop cannot get it in. I did take off the fuel water separator and will change this. The boat was stored over the winter with stabil but the 55 gallon tank probably only had about 15 gallons in it. Is moisture causing this problems? but like I said it ran fine below 4000 RPM/ Please Help!!!

 

[Don S]

Re: PLEASE Help! Mercruiser problems above 4000 RPM

When you change your fuel filter, take the old filter and pour the contents into a clear container and see if there is any water in the fuel, and if there is how much.
Next. Is this the first time you had the boat out since you owned it? IF not, did it work ok last season?
How long since a tuneup?
Have you considered putting more fuel in it?
Might be defective tach, and you are actually hitting the rev limiter.

 

[Wyomingman]

Re: PLEASE Help! Mercruiser problems above 4000 RPM

Thanks Don S for the reply. I have owned the boat for 3 years and it ran fine when winterized last fall. No problems at all last year. I already disgarded the old water sperator filter and replaced with a new one. It did seem to have some water in it although i did not put it in a clear container, wish I would have now. The last boat tune up was in 2009. I probably have about 30-40 hours on it since then as I don't use it that much. I did put about 10 gallons in before I took it out over the weekend. I put two cans of sea foam in and I will fill the tank up as it will probably hold about 40 more gallons.