1988 Mercury 50hp Intermittent Cranking Problems

gwpjr

Cadet
Joined
Jul 25, 2012
Messages
17
Hey everyone. Recently my 1988 50hp developed a perplexing gremlin: Twice now I've had the motor refuse to turn over. No click from the solenoid, nothing. The first time was after it was running for a bit and I pulled in to the dock to change the trim pin to a different setting. I trailered the boat back home and ran some diagnostics. I tested the solenoid and found 12v from the battery on the high voltage input, 12v to the low voltage post when the key was turned to start, continuity between the ground post and the engine, but no voltage on the starter post. After letting the boat sit over night, it turned over no problem. Thinking that the solenoid was sticking, I replaced it and had no problems with the boat the next day on the water, even after starting and stopping the motor several times while fishing.

Today at the ramp I tried to start the motor and it caught twice, but didn't stay running once I let off the choke. Normally it will stay running and I only need the choke to start it. The next turn of the key: nothing. No clicks. I manually bridged the starter posts and it turned over, but wouldn't catch. Strangely, this time the tach isn't returning to zero with the key on either. I haven't had a chance to run through the usual electrical tests yet.

Up until now this motor has been very reliable with no problems. The only thing new is the tach that i added, but I can't see how that would be causing the problem; it isn't even in the starting circuit. I'm posting here in case anyone has any ideas that might help.
 

gwpjr

Cadet
Joined
Jul 25, 2012
Messages
17
Re: 1988 Mercury 50hp Intermittent Cranking Problems

Ok. Once I got the boat back home I found that the fuse on the 12V from the solenoid was blown. After replacing it she turned over and started. I hope that is all it is this time. Guess I'll have to add spares s for this fuse to my in-boat gear. While there was no obvious reason for the fuse to blow, can anyone think of anything else I should take a look at?
 
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