2002 Crusader 8.1 standard on my 39 silverton MY. Had a number of problems with port engine in past subject of posts in 2011. Only about 250 hours on engines as for past several years it only goes out a couple times a year. When first purchased boat WOT was about 4400rpm with cruising speed at 3600 rpm and about 24mph. Last year and this year boat runs fine except it maxes out at full throttle on both engines at only 3500 rpm and 20 mph while running. In neutral engines will rev to about 4400. Really puzzled as two separate fuel tanks. Starboard engine is original equipment except for impeller while port has had new ECM, fuel pumps, fuel filters, etc as a result of stalling problems. Last attempted cruise yesterday, was running at 3400 and 19 mph but was able after about half hour run to coax to 3500 rpm and 20. 7 mph. Mechanic at shop says probably just algae build up on bottom but sounds fishy to me. I run in Lake Erie and put 125 gallons fresh fuel in yesterday. All fuel from local marina and no ethanol (at least thats what is advertised). Help and thanks in advance for any suggestions.