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1994 Merc 50/60hp - Burning electrical smell

MnSkip

New member
Alright guys motor was working great until i let a buddy borrow the boat....spare me, i know...

So the story goes he was having trouble with the fish finder so he put a second battery in the boat to run the fish finder separately. Come to find out that second battery was dead so he had the bright idea of starting the motor, switching battery cables to the dead battery, and run the fisher finder on the good battery. He did this because the motor alarm would go off when he disconnected the battery, well no duh.

He says when he switched the cables to the dead battery the motor alarm slowly died out, the motor died and he could then smell a slight burnt electrical smell he says originated on the right side of the motor (right side if you were looking at the front of the motor while sitting in the boat). At which point the motor would no longer start or run.

I haven't had time to dive into it yet, but i was hoping you guys could give me a good idea on where to start.

To summarize, while the motor was running, he switched the battery cables to a battery that was apparently dead, the motor alarm died/motor quit running and he could faintly smell burnt electronics from the right side of the motor. Motor will not start.

TIA
 
This is 5 days old so it may be too late. The Mercury service manual clearly states that you do not unplug the battery, much less plug it back in, or worse yet switch leads while the engine is running...on switching leads, never...... The charging system is probably what you smell, rectifier/regulator module and possibly the stator windings. On why it won't start otherwise it depends on how the 12v is routed through the engine, in particular feed to the ignition switch box or modules.
 
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