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Nessmuk

Optimax quitting

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I've got a pair of 2003 150hp Optimax motors, one of which is giving me problems. Seems to run fine unloaded, but when hitting about 3000-3500 rpm under load the motor quits without warning. No sputter, no odd noises. Just quits. Temp seems OK. Water is moving. Fuel flow matches the other motor. Will restart immediately. On occassion it will run to max power.

 

I have verified the primary electric and low pressure pumps are working, at least on the trailer. Water sep fuel filter is fine. I get no warnings on the smartcraft gauges. Gut check says sensor/electrical, but what do I know?

 

Anyone have any experience with this? Otherwise I've got to get it to a mechanic this weekend. Can't stand it anymore.

 

Incidentally, I've had good experience with Silver Spring marina down in Wakefield, unless any other Rhodies know a great Merc mechanic down around here I should try instead.

 

Thanks folks...

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I had the same problem a couple of years ago. It would idle fine but once I tried to give it a go. It would simply cut out on me. Turned out that the low pressure pump was shot.

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Could be a short in your high speed stator coil. Most ignition systems use two stator bobbins with different gauge wires. One generates voltage easily at low rpms, and one kicks out voltage at higher rpms. Together, their voltage curve is constant throughout the rpm range. If the high speed coil is bad, it'll start right up, but around 3000-3500 rpms won't generate enough voltage to fire your plugs, and it's just like turning off the key. However, I'm not sure why it would occasionally run to max power if that was the case.

 

You could try swapping stators and seeing if the problem jumps follows it to the other outboard before shelling out $$$ for a new one.

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That's exactly what it's like, shutting off the switch. I'll see if I can't swap them like you suggest. The things runs like a top until reaching 3000 rpm.

 

I check it again in neutral too. A bad stator should be a problem no matter if the prop is loaded or not, correct? Strictly a matter of RPM rather than load?

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View PostI check it again in neutral too. A bad stator should be a problem no matter if the prop is loaded or not, correct? Strictly a matter of RPM rather than load?

 

Correct.

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Johnson Boat Yard in Wickford is a top level OptiMax dealer. I think the mechanic's name is Richard or Mike. Very good, they all use black boxes to diagnose these days

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Damn. Just ran it up to over 4500rpm in neutral and it runs fine. Temp only got up to about 115 but I really don't think it's a temp problem anyway. I'm not getting any warnings.

 

I'm going to put it back on the water this weekend and have someone watch the priming ball when I run it. Maybe it's collapsing. It just seem like a fuel problem though. It doesn't cough, it just quits w/o warning. Like electrical is being cut off. And it happens at around the same rpm every time.

 

It would be an interesting puzzle if it wasn't such a PITA.

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