Hey All,

I think this is my first post, but after tons of searching and taking the preliminary steps to diagnose and remediate the issue, I'm at a loss.

The boat: I have a 92 Powerquest with twin 454 mags on B1's. The engines are around 350 hours. Never seen salt water.

The issue: Starter works great when cool, but after running a while and getting some heat into them the port engine won't engage the starter. No clicking, no sluggish turning over, etc. The voltmeter does move when turning the key, but nothing happens until it either cools off or I jump the slave solenoid.

The steps I've taken:
New micro-switch for neutral safety (tested the old one, and was fine, the new one was fine too)
New slave solenoid by the breaker as well
Brand new batteries
New alternator (as of last year)

When I jump the solenoid it cranks and starts up perfectly.

Any help would be great.

Thanks,

Josh

At a minimum, Solenoid on the starter is done as it is suffering from heat sink (takes more amps when hot)... example is #34 ( check your engine serial to verify).... pull the starter and check for corrosion..... any corrosion will increase your problems in throwing out the drive assembly as well and a replacement starter is the long term fix $ for $

https://www.marineengine.com/parts/m.../starter-motor

Thanks, Speicher lane

I figured it was, but before I crawled down there I wanted to be sure. Just placed my order.

When you pull the old starter, be mindful of any shims installed between the starter motor and the block...If you are lucky it;s just the solenoid...

Have you tried jumping across the terminals of the slave relay?
Title says slave and comment leads to starter solenoid

i jump the terminals of the slave relay and it starts up. The slave relay and micro switch are both new

Then there is a break on the power side or ground side

If you turn key to start and get 12V on the small yellow/Red wire on bottom of slave relay then the power side is good.

If power side is good, the there is a small Black wire across from the small Yellow/Red, it goes to ground. Check the ground

excellent point. that would mean when I jump the slave to complete the circuit to the solenoid and it cranks over then the solenoid is fine wouldn't it?

I'll let it ride as is and next time it does it i'll get my multi-meter out and test the wires. I attempted to take the starter off this weekend. Holy h&*l that is by far the biggest PITA i've ever encountered in my wrench turning years. One task that I think i'll pay someone to do. (twins in a non-staggered configuration)

Correct, there is no issue with the starter solenoid or starter for that matter

So it wasn't the starter. I spoke with a seasoned mechanic at the marina and he just fixed a boat with the same issue. I haven't confirmed yet but he said it is most likely in the wiring harness connection on top of the engine. He said after a while the connections/pins will degrade or bend enough so that they will still be conductive but the connection is so weak that it won't support any voltage. (i'm sure i've more than once pushed against it while trying to wriggle my way out of the bilge)

I'll try and fix this and follow up so that in the future anyone with the same issue will have a reference.