Need ideas on problem with 5.7L Mercruiser shutting down

[alldodge]

Where is the 10-point connector?

not 10 point, 10 pin connector
It is at the rear of the motor on top. It's the engine harness connector and usually has a clamp keep it connected

 

[NuthinFancy]

not 10 point, 10 pin connector
It is at the rear of the motor on top. It's the engine harness connector and usually has a clamp keep it connected

Thanks...42 years in a tractor-trailer and I'm learning about boat engines!

 

[QBhoy]

Not charging is a completely different issue.

Hi Scott..are you meaning you think it’s not the issue or just pointing out that it’s a separate possible cause from an earlier suggestion? It would be at the top of my list of possible causes, given the details given.

 

[Scott Danforth]

Shutting down is one issue

Not charging is a separate issue

 

[stresspoint]

any result yet ?.

 

[NuthinFancy]

any result yet ?.

Thanks for interest, stress point. I have not been able to try anything yet...very pleasing to find so much help here. I'll post when I determine something. Keep the bottom wet and top dry!

 

[redneck joe]

I had a 79 that would run like crap and or die after running. Turned out just needed new plug wires. Of all the things i did to her never did the wires mechanic said prob original. This was about five years ago. Added electronic ignition while we were at it. However not turning over is something else. Could have two issues.

 

[NuthinFancy]

I had a 79 that would run like crap and or die after running. Turned out just needed new plug wires. Of all the things i did to her never did the wires mechanic said prob original. This was about five years ago. Added electronic ignition while we were at it. However not turning over is something else. Could have two issues.

Thanks Joe. It runs great and never any probs. Then, the last time out, abruptly quit running after approx. 30 minutes. 3hrs later started with no prob.
Haven't been able to try some of the fixes suggested here...very pleasant surprise at all the response.

 

[scatgo]

Any luck?

 

[NuthinFancy]

Any luck?

Thanks for interest, scatgo. Wife is very ill and I've not had chance to go to boat. I'll post as soon as I determine something. Remember: bottom wet and top dry.

 

[tank1949]

while friend at helm and in the dark with muffs on or at dock, start wiggling wires. I suspect coil wire grounding out.

 

[scatgo]

Thanks for interest, scatgo. Wife is very ill and I've not had chance to go to boat. I'll post as soon as I determine something. Remember: bottom wet and top dry.

Sorry to hear about your wife. Prayers sent. Let us know how it all goes. Peace

 

[NuthinFancy]

while friend at helm and in the dark with muffs on or at dock, start wiggling wires. I suspect coil wire grounding out.

Thanks Tank...I'll let you know.

 

[THenning]

When this happened to mine, the ignition coil was bad. Ran till the coil warmed up then died. Would start again and run when cold. May not be the issue but something to check.

 

[NuthinFancy]

When this happened to mine, the ignition coil was bad. Ran till the coil warmed up then died. Would start again and run when cold. May not be the issue but something to check.

Thanks, TH. It certainly could be...you describe my problem exactly. I'll let you know...and thanks for prayers.

 

[NuthinFancy]

Sorry to hear about your wife. Prayers sent. Let us know how it all goes. Peace

Thanks,

Sorry to hear about your wife. Prayers sent. Let us know how it all goes. Peace

I appreciate it, scatgo. Will do.

 

[stresspoint]

i had a strange thing happen with a tb ignition on my 4.3 , motor would randomly cut but randomly start again and run perfect.
never got to the bottom of the cause BTW.
my story : drive the boat motor cuts , check over all the usual suspects , no start , then out of the blue it would start and run perfect random amount of time and cut again.
more diagnosing to no end .
while someone else cranked the motor i pulled the coil lead at the cap , no spark TILL i had about 3/4 an inch between , the motor would then start and ran perfect until i closed that spark gap , then it would stall out an not start again till i opened that gap again.
it still has me bewildered till this day what was going on there "" i changed out the ignition system and did not bother to deal with it any longer because i was wanting a reliable boat that has a basic ignition system.

 

[NuthinFancy]

i had a strange thing happen with a tb ignition on my 4.3 , motor would randomly cut but randomly start again and run perfect.
never got to the bottom of the cause BTW.
my story : drive the boat motor cuts , check over all the usual suspects , no start , then out of the blue it would start and run perfect random amount of time and cut again.
more diagnosing to no end .
while someone else cranked the motor i pulled the coil lead at the cap , no spark TILL i had about 3/4 an inch between , the motor would then start and ran perfect until i closed that spark gap , then it would stall out an not start again till i opened that gap again.
it still has me bewildered till this day what was going on there "" i changed out the ignition system and did not bother to deal with it any longer because i was wanting a reliable boat that has a basic ignition system.

Man...that was strange. I still haven got back out to mine...checking the coil will be a good place to begin. Thanks, stress point.

 

[stresspoint]

Man...that was strange. I still haven got back out to mine...checking the coil will be a good place to begin. Thanks, stress point.

yea mate , very strange , i should have taken a vid as no one i have mentioned to has had any idea either what was the cause.
suggestions have been:
crack in cap.
crack in rotor contact in the cap.
water intrusion in the lead. .
broken carbon lead .
+ many other could have beens .

 

[Scott Danforth]

The 2-wire ignition sensor mentioned in post #4 is more probable than a bad coil.

And a simple trouble shooting guide exists to test the system (also linked in post #4)