Mercruiser 4.3L shuts down all electrical

[lolasowner]

I've had two instances of losing electrical power to everything in our boat except for the trim. The first time we had been on the water for a couple of hours and I was starting the engine when it just shut down all power. The second time we were cruising at about 20MPH when everything shut down and there was no power. In both cases, by the time we brought the boat home, all power was back and the engine would start fine. I'm thinking it might be related to the 50A overcurrent protection circuit, but I'm not sure if that breaker would kill all power in the boat (and I can't reset it with any success)? I did notice that the oil gauge was bouncing erratically prior to the most recent shutdown, so I am suspicious of a short circuit somewhere. What would cause all of the electrical power to shut down to everything except the trim?

 

[scipper77]

Re: Mercruiser 4.3L shuts down all electrical

sounds like an ignition problem to me. From what you describe it sounds like it is acting as if the key was switched to the off position.

 

[Bondo]

Re: Mercruiser 4.3L shuts down all electrical

Ayuh,... Sounds like a Ground problem maybe.... Could be the big Cannon plug too....

Get yourself a multimeter,+ When it dies,...
Then start checking Where there's power,+ Where there Ain't....

 

[owens76]

Re: Mercruiser 4.3L shuts down all electrical

I had the same problem on my 1985 4.3 185. It was the Cannon plug. I orded a new wiring harness from the engine to dash board. Problem solved, and easy to install.

 

[lolasowner]

Re: Mercruiser 4.3L shuts down all electrical

Thanks for the quick replies. I will look at the Cannon plug and wiring going back to the engine. If there is an ignition problem or if the cannon plug is causing some problems would those literally prevent all power from everything except the trim? I've noticed that even the blower doesn't run when it is in this condition, and that normally works even without a key. If the blower works, then the boat will start and run fine...until it quits again. If the 50A protection breaker trips will that have the effect of eliminating all power to every subsystem?

 

[rbh]

Re: Mercruiser 4.3L shuts down all electrical

hey there-
your trim motor is probably connected directly to your battery, if the battery cables are loose or dirty you can have intermitent outages due to expansion and contraction, clean and tighten both sides, positive and negative, as well do the same to your main battery switch (positive) and all grounds
rob

 

[owens76]

Re: Mercruiser 4.3L shuts down all electrical

hey there-
your trim motor is probably connected directly to your battery, if the battery cables are loose or dirty you can have intermitent outages due to expansion and contraction, clean and tighten both sides, positive and negative, as well do the same to your main battery switch (positive) and all grounds
rob

Rob is correct trim power is separate of the engine power, when connected to the battery. There are 8 to 10 pins in that Cannon plug, mine had one of the male pins cracked and bent. If you would wiggle the plug then all power would be restored. Let me know if you need the website where I purchased mine.

 

[gadget73]

Re: Mercruiser 4.3L shuts down all electrical

Also check the connections on the side of the starter. Main + feed goes to the solenoid on the starter, and there is usually either another wire feeding out to the rest of the boat, or a fuse where that power is fed from. If the connection there is questionable, it will work when it feels like it. Pull and clean your battery connections too.

 

[P 0 P E Y E]

Re: Mercruiser 4.3L shuts down all electrical

These guys are right on. If you loose all power, it is most likely your ground or positive main.

First, turn on a load or circuit that will talk to you when you find the loose connection. You could have an assistant hold the horn on or turn the key to start position while you wiggle all the wires. If you wiggle the problem, it may talk.

I like to use a good pair of jumper cables to aid in the troubleshooting of these kinds of failures. use the black wire go from ground on the battery directly to engine metal and see if this fixes. If not use the red wire, directly to engine starter.

If you have a load tester you can use it with jumper cables to test to see if the problem is in the ground or in the hot wire.

Its best to trouble shoot the failure, when the engine is in the failure mode.


Forest inspect your battery connections for tightness be careful because they may be hot at the point of highest resistance.

Next check the engine ground and positive wire for tightness.

 

[lolasowner]

Re: Mercruiser 4.3L shuts down all electrical

Just wanted to close the loop and say Thank you for all of your help. I turned on the radio to talk to me and started going though the wiring from the battery and as soon as I touched the big cannon plug the power went out. Turns out it was not seated all the way and just barely making a connection. I tightened it up and all seems fine. thanks again!