Electrical Issue

[KScott78]

Hello, I've got a 1989 Force 125hp that I just purchased used ( I'm not a mechanic ). When connection the battery I know the cables are getting hot. After some testing with my multi meter I've found the that issue appears to be with the starting motor, when it test resistance from the positive terminal on the starting motor with the ground on the block I'm getting a beeping ( sorry not sure what the correct term is ). When testing I disconnected the main power wire from the starting motor. So it appears that it's grounding out. Does this mean I need a new starting motor? Or any other ideas how to fix this?

Hope this makes sense, thanks!

 

[Frank Acampora]

Not sure if I read you correctly. If the cables get hot as soon as you connect them then there is a short either in the starter itself or in the relay,

The starter motor uses MASSIVE windings and the resistance from positive terminal to ground should be almost zero. The brushes may be worn or the commutator may be carboned. Either condition will raise resistance. A broken winding or two will slow the starter.

Hot cables are generally due to the starter motor turning too slow. As explanation: When an electric motor turns, it not only uses current from the battery but acts like a generator and develops what is called "back EMF" (Electromotive Force). This is a reverse current limiting the amount of amperage drawn from the battery. When the motor turns too slowly for whatever reason, the back EMF does not get generated and amperage from the battery gets higher than the cables were designed to handle. Thus they get hot, most usually at the connection.

Remove the starter motor and disassemble it You don't need to be a mechanic. Look at the windings to be certain none are broken or burned. Look at the brushes and commutator on the bottom and see that they are not worn or really dirty. The commutator should look bright copper where the brushes touch it.

 

[KScott78]

Thanks for the reply! I'll take the starter apart and have a look. I'm replacing many of the rotten wires on the motor and it's now running. Still a few issues but making some progress. thanks again