'94 Merc 225 OB w/ Carbs - Cuts out and Surges in rough water

[mluns1]

Mounted behind the transom of a 22' Boston Whaler Outrage on an extented Gil bracket. In rough water on Lake Superior the Merc 225 cuts out at lower throttle positions. To maintain headway in rough water (waves of 3-1/2' to 4' or higher) the throttle has to be at nearly it's full position to keep the engine running and the OB consistently accelerates going up a wave, decelerates or cuts out going down. Fuel tank was at least 75% full on these occasions. Merc dealer rebuilt carbs, replaced all coils, replaced throttle position sensor and tried a new computer with no effect. Fuel primer bulb didn't appear to be collapsed during surging. Water seperator filter was replaced twice and poured into a glass jar to check for water. No water was found. First incident - found some water under the engine cowling. Caulked gap in the engine cover gasket. Next time almost no water was found under the cover. The tilt of the engine affects how smooth the engine runs at idle. In smooth water the engine runs well at all throttle positions.

 

[Waterbugtoo]

Re: '94 Merc 225 OB w/ Carbs - Cuts out and Surges in rough water

22 footer in 4'+ waves? You must like it rough. LOL<br /><br />That sounds severe enough to cause the fuel to run out the front of the carbs instead of into the motor. Same as when you tilt motor up and down.

 

[clanton]

Re: '94 Merc 225 OB w/ Carbs - Cuts out and Surges in rough water

I did not know that the carbuator engine had a throttle position sensor or computer. Could it be EFI engine?

 

[mluns1]

Re: '94 Merc 225 OB w/ Carbs - Cuts out and Surges in rough water

3-1/2 to 4' waves are just a good walleye chop here. The 5 to 7 footers aren't much fun but that's when you really need an engine that performs well. <br /><br />I thought about gas not being drawn into the engine however engine vacuum should be sufficient to draw in the fuel/air mixture or else how could carbureted airplanes fly upside down and do loops.<br /><br />Furthermore,if engine attitude were a big factor this would be a consistent complaint of every non-fuel injected outboard user who's ever been in rough water.<br /><br />I guess the next step is to splice in a clear section of fuel line and have another person on board to monitor the fuel flow during surging. Also I could put in a T valve which could be used as a switch to pull fuel from an auxillary tank to see if that corrects the problem during rough water. If the tank or line is not the problem maybe they screwed up on rebuilding the carbs, or it's drawing water in the carbs somehow. An electrical problem doesn't seem likely.

 

[Hooty]

Re: '94 Merc 225 OB w/ Carbs - Cuts out and Surges in rough water

I think the first thing I would look at is the float level in the carburetors.<br /><br />c/6<br /><br />Hooty