RPM fluctuation

[Ed Shankle]

After a few hours of steady motoring through calms this weekend, the RPM's suddenly dropped from 2500 to 2200. After a minute or two it went back up to 2500. Did it a couple more times during the next 15-20 minutes. Shut the engine off and sailed for the rest of the trip back, except for a short duration through the mooring field, as the wind had returned.
Is this a symptom of anything I need to be concerned about? Engine temp was steady; no visible signs of water or crud in the Racor bowl; the fuel pump is after the Racor.

Ed

[Ron Hill]

Ed : Are your Racor and engine fuel filters fairly new?  Is the screen out of your fuel pickup tube?  Is your throttle linkage slipping?  How dirty is the inside of your fuel tank?  Has it ever been cleaned in the past?
A few thoughts.

[Ed Shankle]

Hi Ron,
Racor new this year; engine filter last year; no screen on pick up tube, new fuel tank this year. Linkage doesn't appear to be slipping, besides it returns to the original RPM, so I assume linkage is not the problem.
Any other thoughts?

Ed

[ajvh]

A couple of months ago, I was motoring along when the rpm and speed dropped significantly. I thought that I had hooked a crab pot. There was also black smoke coming out of the exhaust. It turned out that the insulation was blocking the air intake to the engine. I turned the intake by 90 degrees and the problem went away.

Maybe you have partial blockage of the intake?

[Ron Hill]

Ed : The only thing that will make an engine "motor" is a change in fuel.  

[Stu Jackson]

Ed

1.   Has it happened again?

2.   Try a search on "electric fuel pump."  Ours died slowly, as noted in that post of mine.  I just posted that reference on another thread.