Hi all, new owner of a 2004 Carver 360 Mariner with twin 5.7 MPI's.
Sea trial no problem. First hour and a half of drive home after purchase was perfect at 3,600 rpm. Both fuel tanks registered at 1/4 tank (125 gal each). At this point the starboard engine started stumbling badly and revs dropped way down. The captain thought that maybe the gage was incorrect and we were running out of fuel so we stumbled in on the port engine to get gas. Put in 60 gallons each tank and the gages both went back up to over 3/4. Started right up and we continued the voyage. Ran great again so we assumed problem solved. Ran another hour and the same thing happened. At this point we were only a few miles from home and we knew we had fuel so he dropped the throttle way down on starboard and ran 80% on port engine. After a couple more miles and nearing home port, the starboard engine started running smooth again. We ran the rest of the way at a reduced speed and got into port nicely.

Note: new fuel pumps and fuel coolers installed this past winter by P.O. Only about five hours this season.

I read through a lot of posts here and have seen several similar issues pointing to several solutions. What I'd like to hear opinions on is the best sequence to start the trouble shooting process. Possible ideas from what I've seen here and elsewhere:

1. Fuel Polish
2. Large particle filter/water seperator
3. Small particle filter before pump
4. Anti-siphon valve (not sure if I have one)
5. Fuel Vent tube
6. Fuel pressure
7. Something else?

Thanks.
RyDrew