No power to ignition switch, other electrical still works

[KetchiMan]

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

 

[alldodge]

removing/replacing the alternator.

You might have blown the 90amp fuse on top the starter. In any case your going to need a volt meter to see where voltage is not. Suggest starting with the 90amp fuse (item h)

 

[Bt Doctur]

see if you have voltage at the orange output wire, if not the 90A at the starter is blown. If you find a Red wire also on the same post cut it away and piece it out directly to the starters main post. The Red wire is the main system power feed and is protected by the 50A circuit breaker. You dont need a 90A fuse in front of it.

 

[achris]

In 'Alldodge' diagram item b is a 20A fuse. It's a glass 3AG fuse and its holder. I have seen quite a few of those with corroded terminals cause the problem you have. I always replace them with the water resistant blade fuses, like so....

It then also matches the fuses on the engine, so you only need to carry one spare fuse to cover all.

Chris........

 

[KetchiMan]

Thanks for the help. I just pulled the 90amp starter fuse and it is bad.
I love this forum!!!

 

[TimTJR]

see if you have voltage at the orange output wire, if not the 90A at the starter is blown. If you find a Red wire also on the same post cut it away and piece it out directly to the starters main post. The Red wire is the main system power feed and is protected by the 50A circuit breaker. You dont need a 90A fuse in front of it.

So you can just remove this 90A fuse and connect the red wire to the starter and the 50A circuit breaker will protect it? My motor has this 90A fuse but have not had any problems with it yet. Should I go ahead and remove it before I do have problems?

 

[Bt Doctur]

The Red wire is main system power and is protected by the 50 A CB, the alt is protected by the 90A fuse link.
You experienced what happens when the link blows for whatever reason.Your dead in the water. With the Red wire to the battery post on the start you have power to start and run the motor but do not have the alt charging.
Extend the Red wire to reach and leave the 90A on the orange wire only.

 

[GA_Boater]

Closed. A couple of years old.