7.4L MPI dies when the boat hits a wave

Js98Snake

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Apr 29, 2006
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My boat is a 2001 Checkmate 218 Persuader with a 7.4L MPI. Somewtimes it will start without giving it any gas right away but then die imediatly...kind of like it's not getting fuel. Other times I have to give it almost half throttle and it still turns over 5-6 times before it fires. Today we were out in the Gulf and everytime I hit hard from a wave it would die. It would start right back up and then 30 seconds later I would hit another wave where the hull kind of slams and it would die.<br /><br />I replaced the fuel/water separater today, and I can hear the electric fuel pump prime up everytime I turn the key to the on position.<br /><br />Here's what I'm thinking:<br />-bad fuel pump<br />or<br />-there's a hidden fuel filter that if clogged (not the big fuel/water separater that looks like an oil filter)<br />or<br />-some sort of lose connection since it would die when we'd hit a wave, but then I don't know why it does the same thing when in flat water.<br />or<br />-computer problem<br /><br />Anyway I'm looking for a starting point to trouble shoot. I know where the fuel pump it, but it look's damn near impossible to get to.<br /><br />Thanks Jake
 

Js98Snake

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Apr 29, 2006
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Re: 7.4L MPI dies when the boat hits a wave

One more thing I was just thinking...could this be an ignition problem? When I got back to the dock yesterday she was runniny real rough. Maybe a bad or cracked dis cap, worn rotor, coil going out ect...
 

Js98Snake

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Re: 7.4L MPI dies when the boat hits a wave

Final note the boat was sitting for 1 1/2 yrs.
 

Don S

Honorary Moderator Emeritus
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Aug 31, 2004
Messages
62,321
Re: 7.4L MPI dies when the boat hits a wave

Sounds like a loose electrical connection. Start it up and do a wiggle test on all the sensors and connections. <br />Is this a Mercruiser or Volvo?
 

Haut Medoc

Supreme Mariner
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Jun 29, 2004
Messages
10,645
Re: 7.4L MPI dies when the boat hits a wave

I agree with the loose electrical connection....<br />I would look for any obviously cruddy connections & clean every connection dealing with the ignition, as well as performing Don's wiggle test......<br />I would do Don's test first though to try & isolate exactly where it is....<br />It might just be the one that is next to impossible to get to...(Murphy's Law) :mad: :) The make & model would be good, as well, some makes models are prone to different problems ;) .....JK
 

Js98Snake

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Apr 29, 2006
Messages
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Re: 7.4L MPI dies when the boat hits a wave

Well I put new plugs and a new coil in it...the old coil had some sort of gunk all over the male end and the coil wire was full of the shat stuff on the female side. Boat ran like a top, no problems at all. It died once and we hit plenty of waves. I'll continue cleaning all the electrical fittings.<br /><br />Boat is a 2001 Checkmate 218 Persuader<br /><br />Thanks<br />Jake
 

bigbrownbuku

Master Chief Petty Officer
Joined
Sep 17, 2004
Messages
885
Re: 7.4L MPI dies when the boat hits a wave

the main harness plug should have a clamp on it and be completely seated. the mpi requires no throttle to start.
 
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