Perkins M50 Starter not engaging

[svdate]

Greetings. Hoping someone has some insight into why my starter motor sometimes just whirs without engaging the pinion gear.

1) I bought the boat in 2008 and actively sailed her 2.5 years, across the Atlantic and back, no issues, ever, with the starter.

2) I put the boat on the hard in 2011, and then, along with other major work, had the engine pulled and overhauled in 2022. The work was finally complete in May 2023, and the engine was reinstalled.

3) Immediately during sea trials the starter began, on occasion, whirring but engaging the flywheel. Other times it would engage and start right up.

4) I cleaned all the electrical connections but that did not seem to change anything.

5) At some point over the summer I spoke to you and you suggested it was a mechanical problem, something preventing the pinion gear from sliding along the shaft to engage the flywheel.

6) I pulled it off, cleaned it the shaft as best I could, put it back on, still had intermittent failure to engage.

7) I remembered I had a spare starter aboard and swapped it out. It worked perfectly, every time.

8) To try to troubleshoot further, I tested combinations: Old starter, new solenoid, new starter, old solenoid. This seemed to narrow it down to the starter motor, not the solenoid.

9) I left the new starter/new solenoid combination on and had no problems the rest of the summer and fall.

10) In late December, while prepping to winterize the engine, my son accidentally started the motor in gear.

11) After I shut it down to open the raw strainer so we could pour in the antifreeze, we went to start it, but it only whirred without engaging. This was the new starter, which had worked perfectly until then.

12) After multiple attempts with the pinion never engaging, I removed the new starter and reinstalled the old starter. I engaged on the first attempt. I quckly put in the antifreeze without doing any further troubleshooting.


So two questions:

A) Can starting the engine in gear possibly damage the starter motor?

B) Does the solenoid activation from the white/red wire simultaneously spin up the motor AND power the electromagnet to engage the pinion gear? Or do those two functions happen from two separate wires?

I'm wondering if maybe the problem is the start or ground relays and not the starter motor itself?

Appreciate any insights.

Thanks.

[Don C L]

Did you see any damage to the teeth on the new starter you pulled off? Can you see all the teeth on the ring gear?
You can also check the voltage getting to the starter and any possible wiring problems from the battery to the starter too.

[skipperpete]

Your M50 is unusual, it’s “insulated earth” and that makes troubleshooting extra difficult. Usually the starter is supplied as an insulated earth as OEM but if it somehow got swapped for a “ ground to engine block” starter during its life, it might have a -VE heavy duty solenoid thats setup to give you a brief earth to the block for starting. If you don’t particularly need an insulated earth engine you could corrupt the system by permanently grounding the block but don’t even think about trying this if you have a metal hull, particularly an aluminium hull.
Usually the large solenoid on the starter motor is activated by the keyswitch to first engage the pinion and at that point of travel the internal +VE contacts are joined and full power is then connected and the armature will spin the engine over.