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Old 03 October 2011, 05:27   #1
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Dry Run's Avatar
Country: UK - England
Town: portsmouth
Boat name: Hullabaloo
Make: Humber
Length: 8m +
Engine: 225 Optimax
Join Date: Mar 2011
Posts: 612
Optimax Help?

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?
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Old 03 October 2011, 11:05   #2
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Country: UK - England
Town: London
Make: Ribcrafts
Length: 5m +
Engine: 150hp/2x115hp
MMSI: 235090215
Join Date: Oct 2002
Posts: 2,099
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Is it accompanied by a buzzer? (Overspeed warning)

It could just be cavitation.


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Old 03 October 2011, 11:39   #3
Country: UK - England
Town: bicester
Length: no boat
Engine: outboard only
Join Date: Feb 2009
Posts: 853
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 .
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