3.0 140hp inline 4 cyl. Mysteriously stops working

[4327]

Good morning all. I've had this issue 3 or 4 times now. Driving along and all of a sudden the motor dies. Try to start it right away and no luck. Wait a few minutes and it starts. So this happened again (on Lake Ontario!) when I was about 1km off shore. That's a long way to row. This time I checked to see if there was spark out of the coil by putting high tension lead near the block. I didn't see any spark but not 100% sure as it was real sunny out. But pretty sure no spark. and then 5 minutes later....it starts. Motor temp is OK if not a bit low. Oil pressure OK. Being a 1986 motor, I don't think there are any safety shut offs such as a low oil pressure circuit. Is it possible that the coil is overheating? I know it could be a loose wire ANYWHERE along the wiring harness but I am hoping for a simpler answer. Any help as to where to start would be greatly appreciated. Thanks

 

[Rick Stephens]

Out of the blue like that probably indicates either coil or ignition module overheating. You should probably post serial number and year so everyone knows what ignition type you have. That would help a lot getting you a more informed answer.

 

[tank1949]

Simple fix: go and buy yourself an extra coil, external resistor type high output and install. You need an extra coil anyway. It this doesn't fix it, I suspect module heating up is problem. Also, this happened to me. My Merc OB acted similar many years back. It turned out to be a hidden crack in the main 12 vote power supply cable. Bouncing around caused my motor to stop. I replaced huge 12 volt cable and problem went away! Good luck!

 

[Scott Danforth]

it is rarely ever the coil....ever.....

most likely its the ignition module or the harness plug is corroded or the key switch is bad. easy to trace with a multi-meter

 

[fishrdan]

Mercruiser/OMC/VP 140HP I/O or other? Need more info. Points ignition, did someone upgrade to electronic ignition?

I also doubt it's the coil. That year should have points ignition, which are usually either; running well, runs like carp (needs tune-up), or not at all. Not - running just fine, then dies and won't restart, then after 5 min it restarts and runs well again.

Do you have a multimeter and timing light? These tools will help troubleshoot your issue, when it's happening. Sounds like bad ignition switch or loose wiring to me, but needs troubleshooting.

 

[4327]

I did post Year and model. 1986 140 Mercruiser. 3.0L inline 4. No Module, No electronic ignition. I guess I will carry the multi-meter with me for when it happens again. Probably cant find the issue until it actually happens. Does CAA or AAA cover boats for lakeside assistance / towing? LOL

 

[Bt Doctur]

loosen the camp on the main engine harness plug, spray with cleaner, reinstall and SNUG the hose clamp

 

[4327]

Thanks BT. I will try that too