Multiple slave solenoid replacements on 2000 Mercruiser 4.3

lou23

Cadet
Joined
Jun 19, 2014
Messages
22
I have replaced the slave solenoid on an older 4.3L three times in last year. The last one was an original Mercury part that only lasted about 6 months. Each time after replacing the boat starts fine from the ignition switch multiple times for maybe the next month or so and then stops. Only way to start is to jump the slave solenoid and boat fires right up. I tested the ground at the solenoid and it is good. Also checked the yellow/red and test light shows voltage as well. What could cause the solenoids to fail so often. As soon as I install a new slave solenoid the boat fires right up using the key. Using the troubleshooting guide from Don S. on starting issues I always end up with a bad solenoid. Anyone ever have a similar issue? Thanks.
 

lou23

Cadet
Joined
Jun 19, 2014
Messages
22
Unfortunately my boat is 3 hrs away. I found one of the failed solenoids in a tool bag and tested it with 12 v to activate the solenoid. Nothing, would have expected a click. Nothing to lose so I disassembled the solenoid. The contact disc as well as one main lug were completely black from all the arcing. I can totally see where the diodes would extend the life but mine are failing after maybe 20 starts or so. Also, not getting the single click which would indicate the plunger is activating but not completing the circuit between the main lugs. It seems as though the solenoid plunger is failing, not poor contact due to the arcing issue. I’ve had this boat 4 years and the slave solenoid it came with lasted 3 years (not sure if it was original but I used it 3) before failing. Keep thinking there’s something causing the solenoid/plunger to fail. Thanks
 
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