1985 470- Merc tripping igniton breaker when i turn the key to the on positon .?

Question

I have twin 470s Mercs on my Grady . I disconnected all the gauges that run the port engine, the coil and the choke and it still happens. I also replaced the circuit breaker . The key switch powers the breaker which powers the purple wire that energizes the coil.

Any thoughts would be greatly appreciated.

Thanks

Answer 1

It's hard to diagnose electrical problems but you have a dead short.  a hot (red) wire is touching ground somewhere.  First go to the Battery, make sure your using only one battery, disconnect any others.  then find the main large black engine wiring harness.  All of the wires on your engine lead to the harness.  You will find a plug assembly near the engine.  Disconnect both engines here.  Now check the switch. Then plug in each engine in turn.  That should isolate the problem.  On some boats there is a similar plug at the dash panel.   If the problem is at the engine trace each wire to it's sender or terminal.  check any that touch the block or other wire.  I've seen problems where someone drilled into the harness and put a s***w into the harness.  Good Luck!