Runs & Starts Great out of water, But not in water. Why?

by Rich Fhaner
(Potterville, Michigan)

I have a '87 Mercuiser 140 hp I/O with points and condenser ignition and it is carberated. I hook the out drive up to ear muffs and it start right up. I drive about a half hour to the lake, and it doesn't want to start! and it wants to stall after I start it, as if the the engine was cold. (I just had in running and up to temp a half hour before) As long as I keep it running, It runs like a raped ape! Funny It has done this for the last 7 years I had it. Thanks for any input. Oh, I go in a freshwater lake in Michigan. Rich

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Feb 17, 2013
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STARTS GREAT OUT OF WATER
by: DOUG

Oh, You didn't mention changing coil..They can break down inside after warming up and quit working as they should until they cool back down.

Feb 17, 2013
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RUNS AND STARTS GREAT OUT OF WATER
by: doug

Have you tried to start it at lake "before" putting it in the water? If so, did it run good or was it a hard start? A few second's without water to impeller may not hurt just to see if it starts good or not..If it starts good there, then i'd think theres something to the water pressure idea.But if it is hard to start at water's edge, i'd look inside carb for dripping of fuel into intake making for a flooding problem while inroute to lake or something electrical breaking down after warm-up at home..Google adjusting marine carb while on water for proper carb adjustments to carb.May have something to do with you'r problem also..Again that would be water pressure related as mentioned below.Just a thought

Aug 27, 2011
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i have your answer
by: Anonymous

Your problem is the flaps in the bellows....water is conning in causing pressure and not letting the boat start...when you pull it out the water drains releiving the pressure and that's why it runs good at the time .

Aug 26, 2011
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Ground?
by: Don

I know this is way out there, but if it starts on the trailer but not in the water, could it be some kind of a ground problem? Is there any wiring that could be getting wet, or even be submerged?

Don

Nov 11, 2010
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Starts Hard Off Trailer
by: Rich Fhaner

I have replaced cap, rotor, plugs, condenser and set the Dwell and gap. After I started it on the trailer (runs good) Ran it in the lake (Starts Hard), then took it home and ran it on the trailer, it runs good again. Just not good off the trailer. I don't use the boat, only a few times a year, so it is not worth me trading up. Thanks for the comments.

Nov 10, 2010
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Cantankerous Motor
by: Anonymous

Rich,

Depending on what you've changed out on the engine, but It sounds like some electrical component is breaking down when it gets warm. I would start with replacing the condenser and the coil, the distributor cap, the plug wires and points too while i was in the distributor. 7 years is a long time to deal with this issue. If that don't work, trade it off.

Chuck

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