Fuse Blows When Trying to Start Engine

[arf145]

OK, I've read the Yanmar starting problem threads, but this is different enough to a non-electrician like me to warrant the question:

Yanmar 2GM20F has always started fine--switch on, alarm sounds, one press of the button and it starts. Yesterday, though, when trying to start the engine to bring the boat back in, we got: switch on, alarm sounds, press button, no starter sound and the alarm dies. Then nothing. I found a blown 30-amp fuse in a wire to the starter. Replacement of the fuse, along with cleaning off a little corrosion in the fuse holder, got the power back only until I hit the start button again, which blew the fuse again.

Am I looking at the usual wire issues? Or could it be the solenoid? The connections at the starter look good and clean. Ditto with the connection up at the switch.

Thanks for your help!

[donradclife]

You are on the right track--its either a short in the wiring or an internal short in the solenoid.

To check the wiring, disconnect the end at the solenoid (its the smaller wire). If you try the starter switch and the fuse blows again, its the wire. Alternately, you can check the resistance from the end of the wire to the engine ground--it should be very high.

If the wire is grounded out, you have probably worn the insulation off somewhere and/or it is going through salt water in the bilge.

[arf145]

Thanks Don. I might head out to the boat to do those checks. Could it also be a bad starter button?

[arf145]

OK, I went back for some crude diagnostics. Was able to crank the starter by jumping the terminals of the solenoid. Checked resistance between the wire and engine ground, as Don suggested, and it was very high. I also visually checked for a short and found nothing. So, thinking I had experience a jammed starter, which might now be free, I tried with a new fuse, and it worked fine. Several more starts, all good.

According to one account on the Yanmar site, the yanmar starter drive gear teeth are not rounded on the edges as others are, so the gear can get stuck. Perhaps my nudge took care of this.

[timebandit]

You should be able to hold the starter putton down for a long time with out blowing a fuse. I don't think you have solved the problem.