1975 Merc 500 50 HP - Just Died

[Frankhardt]

This motor has operated flawlessly for years, with proper care & maintenance. This year after normal start the engine just died as if I had turned off the ignition; and will not start again. I suspected a broken wire. Inspected & verified continuity of entire wire harness from control to engine and all is OK. Don't think I have a mercury kill switch, but will look again. My next step is to confirm spark and ohm meter the stator. Two questions: 1. What is the little box that has a Red/green/white & blue terminal connection? (Looks like a small solid state computer) didn't think they had them back then. 2. I am looking for probable causes, because the engine is just too big & heavy to remove and transport for repairs. I would rather start replacing components & hopefully find the problem that way.
Hope someone can help>
Frankhardt

 

[This_lil_fishy]

Re: 1975 Merc 500 50 HP - Just Died

You're on the right track, check spark and compression. Even though you took good care of it....1975 was a looong time ago.


Ian

 

[Frankhardt]

Re: 1975 Merc 500 50 HP - Just Died

Found the mercury cut out switch; it's OK. Stator checks out OK. Found out what the little black box is: (The switch box; untestable without Mercury test gear); However, I also found a faulty diode in the Rectifier. I will replace the assembly, and hope the prob is solved.