Motor & everything suddenly shut down

[DJ_Allatoona]

1986 Mercury 75HP. Yesterday I was puttering along at about 25% power when everything suddenly just shut off: motor shut off and all my electrics went dark: radio, fishfinder, dash. After about 3 seconds, the 12V stuff came back on, but the motor would not start. It turned and turned and turned with no pop. It was as if the kill switch was thrown. I started paddling and got a tow to a marina. After about a half hour of fiddling with this & that I tried the key again and it started.

5 minutes from my launch ramp, again going slow, it happened again: motor and all electrics shut off. 3 seconds later, radio and other 12V stuff clicked back on, but the motor would only turn/turn/turn/turn and not start. Loaded up and before I pulled out of the water I tried the key and it started. About 20 minutes had passed.

Popped the cover and saw that when trying to restart it, the starter motor pinion was not "clicking up" into the flywheel gear. It was already engaged with the flywheel and was not retracting down. So turning the key would just immediately turn the flywheel without that initial "CLICK/REV". It was just "REV". But no start.

Back in my shop I pulled off the starter and installed a spare that I know is good. Tested it and the pinion does raise and fall as it's supposed to.

Background: this is a project motor that has several problems. I got it a few weeks ago after it sat unused in the weather for at least six years. It's running now, and I've been gradually addressing issues as they arise. Lots of things are stuck and rusty and gummed up, etc.

But could this shutdown issue be connected to the starter pinion staying in the "UP" position, or are they separate issues? And what could be the reason the motor would not start, then starts after some time passes? My thought is if the solenoid is bad it wouldn't even crank.

 

[GA_Boater]

DJ - Your problem sounds like an electrical connection is failing - Losing all power and it comes back after it cools down.

I would get the battery tested at an auto parts store and clean all the connections from the battery to the motor, both + and -. Check the connections from the remote to the motor too.

 

[DJ_Allatoona]

Hi Don — I’m out here at the boat reading your reply. Good idea to check all the connections. I’m on that.

Also - I just noticed that one of the two copper mesh grounding straps on the lower back of the motor (either side of the spark plugs) was missing. Rusted away. I pulled one off my parts motor and stuck it on. Wonder if that contributed to my electrical weirdness.

 

[GA_Boater]

Were the bonding straps corroded away or melted?

I ask because poor grounds back to the battery will use the bonding straps to flow current. They aren't heavy enough for starter current and will melt.

I would check all the grounds, one may be loose or corroded.

 

[DJ_Allatoona]

I don’t know if the strap was corroded away or melted. It was missing. Just the terminal end was left attached to the rusty bolt on the block side and I tossed it. The other strap looks OK, just 33 years old. A little crunchy, but still flexible. Do these straps ground certain things/circuits, or do they share the general grounding duties for the whole motor?

 

[GA_Boater]

Bonding straps are for corrosion protection and only handle millivolts and very little current. They aren't for high current at all.

 

[jimmbo]

Your control box has a Deadman Switch on it. It can cause the no start/run issue, but the entire electrical system dying sounds more like connections/cables, even Battery

 

[QBhoy]

I’d be pretty sure that you are describing exactly the scenario which would occur, if your stator/rectifier was faulty. Your basically just running your battery down with it not getting replenished with a charge from the engine. After a wee while the battery will recover enough to fire it...then eventually give in again. What it sounds like to me.

 

[DJ_Allatoona]

I swapped the starter and added an additional ground wire from the starter to the upper right corner of the circuit panel next to it. Not 100% positive that's necessary, but that's the way it was on my older (identical) motor, and not on the project motor.

Also, I added a braided grounding strap from the lower port side of the block to the cowl bracket. It was missing. Started the boat on the trailer and let it run for 20 minutes or so. Starter performs like it should, and nothing cut off or dropped out so...who knows. Maybe I have the grounding sorted.

There is a good condition ground wire between the powerhead and the midsection. I'm not sure if or where there are more ground locations. Can't find the answer to that in my SELOC book.

Test run again on Monday.