Need some serious help!!

[thompsonr]

I'm three weeks in a boat problem and at wits end. The problem is once you get on plane it starts cutting out and loosing power, idles fine starts fine and usually takes awhile to start happening today it ran for about 20 minutes before it started happening the first time it happened happened within a quarter mile, they have thought it was a fuel problem and have replace all the fuel pumps filters. Here is the wierd part as soon as you pull the hood off it runs fine. It is a 2005 225hp Optimax. Any Ideas, would be greatly appreciated.

Thanks everybody for reading

[Hot Runr Guy]

a bit of Googling leads me to an oil level sensor under the cowl. I don't know that motor, but I've read that it appears to have a small reservoir under the hood, with a level sensor that is prone to failure. Maybe, when you remove the cowl when this happens, you do so with the motor tilted-up, and it satisfies the sensor for a while?
HRG

[alanexpup]

that or maybe its not cooling enough.

[toolboy]

I had a similar problem last weekend. The mechanic told me that Mercury had some fuel line that would seperate on the inside, starving the motor of fuel. This would be from the splash well to the motor. After a new line, my motor runs better than ever.

[bloodman]

I had a similar problem last weekend. The mechanic told me that Mercury had some fuel line that would seperate on the inside, starving the motor of fuel. This would be from the splash well to the motor. After a new line, my motor runs better than ever.

Read the same on other posts. Inner line break down from ethanol. May be in pulse pump and fillter. Clear plastic like substance.

[Triton HWA]

You say it runs fine without the hood? take a good look at the air inlet under the hood where the air compressor fitting is. maybe there is something blocking this. Optimax is all about this compressor and running on compressed air. you should also put a guage on each rail connection and see the 2 pressures at the same time adn compare them. if the flat line at the same rate then there is issue in a regulator. 2 guages will tell alot of the story.

[staylor]

...and on an Opti it can be any one of a bunch of sensors or even a coil or ignition trigger. When you pull the hood you do two things- let cold air in, and move/brush the cowling aginst several wiring harnesses all of which have numerous connections- any one of which could be loose when hot or when the cowl is rubbing against it. I'm assuming that you've changed the Opti air filter on the starboard side of the air inlet box on top of the block- if this is clogged then you could be starving for air. In any event, this is something the dealer should be able to track down by pulling the fault data logs from the engine's computer. This should show what wasn't working and exactly when it occurred in terms of running hours. If your dealer does not have the equipment, then find one who does- along with a Merc Certified mechanic. The old fashioned "poke and hope" mechanics should not be let anywhere near a DFI engine.
Doug

[StHubert]

It really seems like it could be a loose wire. I would first check you battery connection making sure the connectors are clean and the nut is tight. If that doesn't work, then I would check the wires right where they enter the engine and by the cowling, looking for a rubbed wire.

[WinnerZ880]

It drove me nuts because it was intermittent and usually happened after the motor ran for a while..
It was a bad spark plug. A cracked plug will work for a period of time until the heat causes the expansion of the pug and it quits working. I had the same problem with a pickup truck once. It would run perfect until I got to a certain road on the way to work and then it would start missing. (about 25 minutes in the case of the PU truck.)

Good luck !!

[thompsonr]

Lots of good replies thanks very much, I just don't know what to think, I took it back to the shop today, I will ask them to make sure they've checked everything.
Thank you very much

[saulteyes]

I had the same proplem. They changed the fuel pump under warranty and it still did it. My problem was the fuel line between the tank and the motor. When i was at full throttle, the line would collapse and starve the engine of fuel. I canged the line and the anti siphen valve and it works perfectly now. The line is not big enough and is too thin. My friend had a similar problem with his engine as well.

[J Ryan]

If your mechanic has'nt found the problem yet, have him check the reeds. They could be cracked or broken.

[mrbreeze]

How old is the starting battery?