Yanmar 3GM30F Fuel Problem?

[Marauder]

I just had to motor back to the marina due to wind right on the nose and needed the short course home. Hated doing it but needed to get back. After 2 hours of motoring at 2500 rpm, motor suddendly slowed to 2000rpm, then after about 5 secs increased back up again. Did this again about 5 mins later, then on and off for the next 30 mins till into the marina entrance. I was ready with the sails if needed and was concerned that if I changed throttle speed I may lose power altogether so left it. A fairly close lee shore was at hand so conscious of also. Made it in to my berth OK, and not sure what the problem is? I had motored for 2 1/2 hours only 3 days ago and no similar problem occured. Today there was a very lumpy sea and boat was rolling all over the place. 3/4 tank of diesel so not running out of fuel as have done this before some months ago. My only suspicion is maybe a blocked fuel filter due to sediment being stirred up? Motor is 10 years old, 650 hours and not sure when previous owner may of changed filters. I have owned for only 10 months. Any suggestions please greatly appreciated

[Morganministry]

If you don't know when the filters were replaced last, then replace them. I would also suspect contamination in the fuel. Water or algae.

Scott

[Badsanta]

I would have the fuel removed from the tank, clean the tank and replaced with new fuel and change filters. Or consider fuel polishing.

[scubasteve]

Replace filter

[Solitude]

Yes replace the filter(s) both primary and secondary. You may want to run it at a little higher rpm. (2900 -3000) see diesel (sticky) here on the site...