1990 Starcraft 180 SFM Electrical

[AeroNautical]

I just picked up a "new to me" 1990 Starcraft 180 SFM with the original Mercury 90hp. I went over everything with the seller and it all checked out. Motor ran great, previous owner just put $1300 into it in anticipation of going on a long fishing trip, when his wife gave him the "okay" to buy a bigger boat. He had receipts to prove it from a local marina. Everything on the boat was clean and in operating order. When I went to take it on the lake today, I lost complete electrical power. I tried 3 different batteries, all had close to 13V on them with a meter. I had to use the electric trolling motor to get back to the dock and didn't even have power to raise the trim. I'm thinking I blew a fuse or broke a ground wire somewhere amd was wondering if anyone had an electrical diagram for the boat so I can chase the wires? I'm also open to any suggestions people familiar with the boat might have.

Thank you!

 

[Texasmark]

Later Mercs and I assume this one too since it is 3 cylinder, Loop charged have a 20 ampere fuse under the bonnet. Remove it and standing on the Starboard side (curb side) of the engine, just aft (to the rear) of the starter is the starting solenoid, having 2 ea ⅜" copper terminals. One goes directly to the starter for starting power and the other is (on later engines) the 12v power distribution point. Attached to that point is the battery cable and red wires from the voltage rectifier/regulator module and another red wire.

Follow that red wire and you should find a 20 amp. fuse under some kind of rubber environmental protector.

The fuse current doesn't power the trim motor but does supply power to "operate" the trim relays/solenoids and all the electrical circuits in the engine, and remote control ignition/trim switches in the remote control box. Auto parts stores carry a variety of fuse types.

If you replace it and it blows again, you need to get a Mercury service manual covering that year engine, which will include an elaborate wiring diagram of everything but your boat unique functions like running lights, and find your source. Possibilities are corroded electrical terminal..."plugs to socket" interfaces...including the fuse to fuse holder itself and other places where chafing could cause the 12v power to short out to the battery (-)....aka ground.

Other than that, it would be a problem where a switch isolates the source and the fuse remains intact until you hit a switch energizing the offending circuit and blowing the fuse.

 

[roscoe]

There is no diagram for the boat.

Motor diagrams are in the motor factory service manual.
You may find one online somewhere.

Power from battery to motor to wiring harness to ignition switch back to motor.

 

[AeroNautical]

Thanks for the replies. I replaced the starting solenoid and the battery terminal connectors because they were fairly corroded inside once taken apart. After that everything fired right up and ran perfect. I'm hoping to take it out soon and see how it does. Thanks again!