Optimax Help?

[Dry Run]

Hi, has anyone had the following problem and managed to sort it? It's driving me crazy! Any help would be appreciated.

Like most of these things, it's an intermitent problem, so not always easy to replicate (when mechanics are here).

the engine is an Optimax 225hp and seems to work well most of the time. However on some occasions (particularly when coming off the top of a wave) the revs suddenly drop by about 500 revs and then start to pick up again back to where they were. I've been from Portsmouth to Cowes at pretty much full throttle without it missing a beat, but then the next trip it's all over the place.

I've had it plugged into the laptop, but no faults are showing (except a water in fuel alarm so have now removed the water and replaced the separator etc).

Anyone had the same problem?

[CJL]

Is it accompanied by a buzzer? (Overspeed warning)

It could just be cavitation.

Chris

[uncle al]

was the water sea water? if so was the direct/air injectors tested indiviually is so could you hear them click ? did they sound all the same?and the same question with the fuel injectors. have you removed and looked at the electrodes on the sparkplugs are they all the same colour?if one is a differant colour put it in another cyl and run the obm remove that differant colour spark plug is it still a differant colour? if so it could just be a knackered spark plug , if the problem hasent moved it could be and i have had this an inttermittant fault on a coil driver, with the number of revs your dropping it sounds like that,try and clean and tighten battery connections , earth connections .
alan