Thread: 2011 Mercury 60HP 4 stroke efi - suppression diode failure?

Hello All,

Has anybody experienced a failure of the suppression diode? I keep intermittently blowing the 15 amp fuse which is the "main power relay/accessories" circuit. Happened 3 times on Saturday - Turn key switch, motor starts and runs for a split second (about the amount of time it would take to release key from start to run) then motor dies. Try to restart and everything is dead - check 15 amp fuse and it would be blown again. Best I can tell is that motor trim is on this circuit as well - checked wiring going to 2 out of 3 switches and wires anywhere that I could inspect. Cannot find any issues. Hoping it is the suppression diode and i have a new wiring harness on the way. Anyone have any thoughts on this?

The suppression diode is located between the brown start solenoid lead, the yellow/red key
switch lead (within the engine harness) and connects to engine ground. The purpose of the
suppression diode is to eliminate the inductive spike created as the start solenoid is de-energized
(key switch turned from START to RUN).
Symptoms of a failed suppression diode:
1. Open circuit - Longer crank times during engine start-up (3 seconds warm engine).
2. Short circuit - Blown fuse #3 (Main Power Relay/Accessory).

Thanks,
Ty

With out more info, sounds like ignition switch. See if you are getting a ground spike at yellow/red wire when key is turned back to run postion