I have twin F225s that usually are flawless. Recntly, and then only very rarely, my starboard motor will act as if it is fuel starved. It drops RPMs and quits or runs rough at 300 RPMs. I have checked the engines fuel filters and changed the Racor water seperation filters. If I squeeze the fuel bulb once or twice the problem goes away. I put about 30 hours on them last week and it happened twice. Port engine runs fine. Both will turn up max RPMs at WOT. I'm buying fuel from a very busy marina and they have not had any reports of bad fuel. I talked to my mechanic about putting them on the shop computer and he said he didn't think it was necessary because the onboard computer would display any issues it couldn't correct on my guages. Engines have 455 hours and the water pumps were rebuilt this spring. Any suggestions?