Am I an idiot? What am I doing wrong?

[JeffreyAC77]

By brother recently replaced his Yanmar starter for about $ 650 (part only).

 

[NorthernFocus]

I'd take it to a starter/alternator shop and have it rebuilt. Probably cost you a couple hundred bucks.

 

[BB marine]

Based on your description below I would have not ruled out a failed starter but not expected a complete starter failure.

Engine will not start. Batteries seem to be fully charged, ignition beeps when I turn it on but when I try to engage the starter, zero. Nada. Not even the click of a solenoid.

The basic circuit is start button, neutral safety switch, start relay. If each of these components have 12V at the terminals, input and output then 12V would be supplied to the starter solenoid mounted to the starter motor. When 12Volts is supplied to the starter solenoid it will activate engaging the bendix gear and the solenoid plunger will make contact to starter motor (connecting the battery to the starter motor. Starter motor is engaged and starts the engine.

The description you described that "engage starter nada not even a click" No voltage drop? But all cables are in good condition and batteries fully charged?
Troubleshoot:

(a)12V @ start switch?
(B)12V @ neutral safety switch? line side
(c)12V @ neutral safety switch? load side
(d)12V @ start relay ? line side
(e)12V@ start relay ? load side
(f)12V @ start solenoid bendix terminal ( small gauge wire)? Solenoid should click
(g)12V @ start solenoid battery terminal? (large gauge wire) Line side
(h)12V@ start solenoid starter terminal? line side connected to starter motor

Good ground connection battery to block, Good round block to starter motor.

Start relay failure will not give code failure.
If all above checks check yes you have a failed starter motor. The motor has an open circuit. The normal indication of this is a solenoid click engaging the starter Bendix but the motor has an open circuit and fails to turn.

If the solenoid does not click there is a good indication that the solenoid has failed. This can be confirmed by test (h)

Troubleshooting from a to h plus always confirming there is no high voltage drop during each test. This is trouble shoot sequence I have used. In many cases the starter is not found to be the failed component. If it is you know you have not spent good money for the wrong reason.

Good luck, If it is a failed starter go with Dans suggestion. If there is not water damage to the starter it is most likely repairable.

 

[2savage]

Well, with a new starter installed (will probably get the original one refurbished for a spare) the engine almost starts. But, the issue now seems to be the electronics control panel that should apparently be isolated but due to worn mounts is grounding out. New mounts ordered. At this rate I should be finished by Labor Day 🙁

 

[ohioan55]

You'll not get a click if the neutral safety switch is not happy. I sometimes need to just bump my lever just a tad so the engine will start. My switch is touchy.