98 speedster engine cutting out

[ganderson]

I have a 98 Speedster with twin 787's, the boat is new to me but has run great for the last 20+ hours. On my last outting the starboard motor started cutting out (loses RPM then revs back up) it will do this for a second or two run fine for a couple of seconds to a couple of minutes and do it again, other times it will run fine for the duration of the trip (30 min+). After the first cut out the tach will die completely then it might start to respond again (usually only after I have stopped), after playing around with it if I pull back the throttle to idle the tach will read properly, if i start to rev the engine again the gauge actually goes backwards to 0. From my limited knowledge I would have guessed this would have been a fuel filter issue but that does not explain the erratic behaivior of the tach??? could this be related to the rev limiter or MPEM? I have checked all the wiring harnesses for loose connections but all seems to be OK, Port engine runs great, no issues at all. Any idea where to start?