Optimax cutting out, water in gas?

[JohnG]

I bought a boat with a 2004 Optimax 135 this past December, hooked it up at the dealership, ran it for awhile on muffs, hooked it up to the diagnostic computer, all was good. Motor has 119 hours of run time on it, all but about 20 hours was at idle.

It was stored all winter long with an empty gas tank with quickleen treatment in my garage which stays about 40 degrees, but does get pretty damp, as it's a tuck under garage. I filled the tank last weekend and took it out, it ran great at idle and even on plane at lower rpm's, but after running for 3-4 minutes at WOT the motor would cut out for a split second, then keep going, then cut out again for a split second, etc. IT would run perfectly smooth again at lower RPM's, but when I'd get back up to WOT it would do the same thing.

Is it possible that I have water in my gas from sitting with an empty tank all winter? Any suggestions on other things I should check?

[ohiojmj]

Take a look at the plugs. You could drain the fuel from the water separator box into a jar and look for water. Check primer bulb, does it stay firm?

I don't know about the smaller optis, but the 3.0s were very sensitive to voltage and would exhibit the same symptoms if the battery was failing.

[JohnG]

The cranking battery is new and I checked the connections, they're tight. I'll check the plugs, is there a safe way to spark test them? can I remove them from the heads and turn it over to check spark, or is that a bad idea?

I would guess it may be a fuel delivery problem, I'll check the bulb and see if it's staying pumped.

[Tim Ellis]

Make sure it has the new ethanol resistant fuel lines and a new fuel filter. If not, alot of guys are having the ethanol break down the fuel line and small particles get sucked into the water seperator and fuel filter assembly clogging them up. Have you pulled the fuel filter and taken a look? Is there fine black/amber gunk present? This website is a great place to get Mercury answers also: http://www.bbcboards.net/zeroforum?id=83 Don Weed is the Mercury Man!!

[REW]

John,
Take the boat out for another run with someone else in the boat.

Go ahead and get it well warmed up.

Have the passenger sit next to the fuel squeeze bulb with his hand on the bulb.

Go ahead and go to wide open throttle. See if the problem happens again.

If the problem does happen again have your passenger just start pumping the fuel squeeze bulb and continue to pump the bulb as you go to full speed and stay there.

With the squeeze bulb being pumped continuously, does the engine cut out?

The reason that I suggest this is that this is one way to distinguish between a fuel and an ignition problem. By continuing to squeeze the fuel bulb you are keeping heavy fuel pressure on the system.

So, I would suggest that if you continue to have a engine cut out issue, that you need to look at a possible power pack issue on your engine - i.e. ignition problem.

I would doubt very much that you have a spark plug issue, because if you did, you would not have a good idle on the engine.
But, you never know unless you check. Certainly a set of spark plugs is a quick and easy thing to change.

I would have thought that with a used rig, you would have automatically installed a new set of plugs in the motor before going out the first time.

Good luck
REW