Mercruiser 5.0 stops all of a sudden like someone flipped the kill switch.

[lawhon11]

My boat cranks and runs fine, but while riding along all of a sudden the motor just cuts off like someone flipped the kill switch. The temp stays around 175. The rpms are running around 3500. It has happened while running at different speeds(10mph, 20mph, 30mph). The oil pressure is around 40(that is midway on the gauge). Once I coast down and put the throttle back to nuetral I can immediately crank it back up. I checked the oil level in the motor and in the drive lube container and both are good. I just put a brand new starter on and while I was doing that I cleaned all the terminals to the starter as well as the two grounds to the motor and all the ones going to the two batteries. What is puzzling is that we may run it all day and it will not die one time, then the next time it may die 4 or 5 times. Let me know if anyone has any ideas, cause so far it has whipped me.

 

[84EdH]

Re: Mercruiser 5.0 stops all of a sudden like someone flipped the kill switch.

Check the main wiring harness plug make sure tight. Also I cleaned all my terminals like you did and had a similar problem. It turned out to be a hot wire that was intermittently touching ground when the boat was under way.

 

[ktbarrentine]

Re: Mercruiser 5.0 stops all of a sudden like someone flipped the kill switch.

Mine was an intermittent open on the fuse at the ignition switch. I swapped out that cheesy fuse holder with a much more substantial blade-type fuse holder. Now it is more reliable and waterproof, to boot! (Thanks achris!).

 

[lawhon11]

Re: Mercruiser 5.0 stops all of a sudden like someone flipped the kill switch.

I will check the harness. I also discovered a red wire going to the battery that has a bare spot, but where the wire is at should not get touched by anything else. Either way I will cut the wire back and put another end on it.