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I have a 2005 Optimax on my 190 Outrage. Engine only has 230 hours on it. Starts fine, idles great. Once I get to 1500 - 2000 rpms is starts bucking likes its not getting fuel.

Plugs have been changed, Filters have been changed. Fuel is not contaminated. No sensors are going off and I had a merc mechanic put the testing machine on and it says all systems are fine.

Any ideas? already missed 1/3 of the season.

Thanks to all who respond.

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What happens when you pump the fuel bulb when it starts bucking?

If it helps, could be a diaphram or failing fuel pump.

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We just disconnected the fuel line and ran the engine on new gas out of a canister. Ran like a charm at high rpms.

The engine is not the issue it seems. Potential 3things this could be:

1) Bad Gas (unlikely as its 75% new gas this spring
2) Its not sucking hard enough to draw from the tank
3) something else

Where is the diaphram on this boat

Are you referring to the fuel pump on the side of the engine?

We are an army working on this right now. Thanks

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Back up a step.

Is the original tank vented?

If restricted it can distort the line and restrict flow.

Presume you are testing engine with a load and not on muffs or reving in neutral.

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on land on muffs

Just removed fill cap

will put in gear and rpm up

no problem there we will relaunch and test under load.


will have someone on board to push bulb if needed.

pumped out bottom of gas tank no water found. more to come

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In water test results

Used a 5 gallon auxillary tank attached to boat engine. Still have pump ball in line. We get under way, 2000 rpm engine starts to break up severely. One person pumping ball and one person driving and no better even with ball hard. We now believe the issue is in the engine while under load.

Please guide us to our next step. Its not the fuel tank, its not fuel cap, as they have been bypassed.

TY

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The Optimax is a complicated, first generation direct injected motor. As a first step, I would make sure any and all routine maintenance has been done, especially replacing any internal filters and cleaning internal tanks. If the problem persists, next step would be to test the output of the fuel pumps - most of these types of motors have a lift pump to get the gas to the motor, and a high pressure pump to drive the actual injection, but I have no idea how that works in an Optimax.

I think your best bet would be to find a mechanic who knows the Optimax inside and out.

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It sounds like you have eliminated the fuel system as the cause. I agree if it is in the motor have a good mechanic check it out as the older injection systems are a bit more complicated. One thing to eliminate is any gray color flexible fuel line if present. The line material is famous for delaminating and collapsing internally causing fuel starvation at higher RPM. Good luck solving an aggravating issue to say the least!

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What pump ball did you use? The original one on the boat?
When was the last time you changed the fuel line a bump ball above the deck?

2005 to 2019 should have new fuel line and fuel bulb replaced.
If they haven't been replaced recently, it is cheap preventive maintenance.