No power to ignition switch, other electrical still works

KetchiMan

Seaman
Joined
Jun 28, 2011
Messages
73
2004 Merc 5.0L MPI, Bravo 3 outdrive in a Trophy 2359
Had just replaced the raw water pump and an idler pulley. Took it out for a test ride and after a few minutes, my voltage reading dropped to zero but everything was still working. A minute later the engine completely dies and all gauges go dead. Now none of the engine electrical works. Fuel pump won't run, starter won't turn and the gauges don't move. Other electronics seem to work just fine. Pushed the main circuit breaker on the engine with no effect. Switched off/on all the breakers at the breaker board. Batteries read 12+ volts. There is no power to the ignition switch or to the little breaker-button that sits below the ignition. It's almost as if the run/off switch is off (but it's not) or as if the throttle isn't in neutral (but it is).

There was an electrical plug up underneath by the raw water pump that I disconnected and reconnected in order to r/r the raw water pump. Don't know what it is, or if it could be related, but it's the only electrical component I touched, aside from removing/replacing the alternator.

Thanks in advance!
-Nick
 

mjf55

Chief Petty Officer
Joined
Jun 17, 2014
Messages
462
Not an expert, but looking at the service manual (#24) in the electrical diagrams, there is a 90 amp fuse on the back of the starter. Perhaps that blew while working. Also, are you sure the connector(s) are firmly together again?

Here is the diagram
 
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