1997 mercruiser 5.7 magnum tournament ski skips backfires and dies

climbabout

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Jun 1, 2011
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Need some help diagnosing a problem. I have a 1997 mercruiser 350 magnum tournament ski - carbureted motor and today on the lake it ran fine for about an hour then started to skip and misfire then idled very roughly and died - could not start it again. Boat did the same thing a couple of weeks ago and in between, I checked the water separating fuel filter and there was no water in the gas (it had a brand new filter from the beginning of the season), checked the fuel tank vent - and no clogs. I also changed the spark plugs, distributor cap and rotor (it has the thunderbolt electronic ignition), I also reset the timing and cleaned the spark arrestor - thinking it was starving for air. The fuel pump seems fine - it looks like it is pumping normally and I can see fuel going into the carb. The boat ran fine in the driveway all the way up to 4000rpm when I tested it, but today it died again on the lake after an hour or so.
At this point, I'm thinking coil?
Any other suggestions from those of you in the know?
Thanks.
Tim
 

Saqbcq

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Jun 10, 2011
Messages
28
Re: 1997 mercruiser 5.7 magnum tournament ski skips backfires and dies

Sounds like that to me. Make sure you replace with OEM or cross-referenced equal some coils are not compatible with Thunderbolt ignitions. Found out the hard way
 

davidrsl

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Apr 11, 2011
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Re: 1997 mercruiser 5.7 magnum tournament ski skips backfires and dies

Tim, if you get the answer, please post it here. I could have written what you wrote. i have a 1998 or 99 (not sure which) that is doing the same. Runs beautifully for about an hour, then suddenly I can't get more than 1100 rpm out of it without stalling. I am suspecting the ignition control module or knock control module but I am less than an amateur at engine diagnostics.

I'll be watching. Thanks!
 

climbabout

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Joined
Jun 1, 2011
Messages
12
Re: 1997 mercruiser 5.7 magnum tournament ski skips backfires and dies

Problem solved - turns out it was the ignition coil. I bought the correct OEM Mercruiser coil and the boat runs fine - fired right up and ran great for several hours and several ski runs this past weekend.
Tim
 

davidrsl

Recruit
Joined
Apr 11, 2011
Messages
4
Re: 1997 mercruiser 5.7 magnum tournament ski skips backfires and dies

Tim,
Thank you very much for following up. I will buy a coil today and try it out this weekend.
Happy boating!
David
 
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