Intermittent Starting Problem

[Chuck Waygood]

"90 percent confidence "? I have been bitten by that ten percent too often to undertake a project like removing your entire galley setup, stove, sink and teak flooring. Look for a "slim" mechanic first, Ron.

[jleonard]

What Chuck said. Plus, I have done lots of boat work "blind" using lights and mirrors (no smoke though). You'd be amazed at what a large mirror can do for you in a tight engine compartment.
The starter has what, 3 bolts? Probably 10mm hex, get a 3/8 swivel socket or wobble extention or both and tie a line around the starter before you start to help get it out.

[seasalt]

I am turning the problem over to the mechanic who replaced the board under the generator. He is hard to get and I should have waited rather than taking a friend's advice to hire the boat electrician who does not do mechanical work. The electrician got down there far enough to attach his voltmeter and place his hand on the starter while his helper pushed the start button. His diagnosis (90%) is that the starter is engaging the flywheel but not turning it. The fact that he got good voltage at the starter and that it only dropped a small amount upon activation led him to rule out loose connections, a bad battery or anything amiss on the instrument panel.

The mechanic who is coming is a very resourseful fellow who will figure out the best way to do what is necessary after he starts his diagnosis back at square one.

Probably the best thing that has happened is that the cranking problem has gone past being intermittent to full time.

[jleonard]

It could still be a loose (or bad) connection or ground at the starter. Voltage is there, but not enough contact to carry the amperage required to turn the starter. It is very easy esp in a marine environment for the block or starter mounting surface that carries the ground to get oily, or rusty/corroded. BTDT in both boats and trucks.
Only trying to help, however......
I'm not yet convinced the electrical circuit is sound based on what I know from this thread.

Replacing the starter may fix the problem, but then you won't know if the scenario I described is true. You could theoretically attach one end of a jumper cable to the starter body and then the other to a good ground point on the block and hit the starter button and see what happens. THAT would rule out the bad ground scenario.
Then you'd have to test the bad pos battery cable to starter scenario. You could do a similar thing going directly from the battery to the starter lug, bypassing the rest of the circuitry.

I am very surprised your marine electricians didn't do things like that. Seems basic to me, but then I'm not a marine electrician, just a gearhead.

[DougSea]

Hey Ron,

Jay's post is spot on. Answers some of the "90%" questions. Crawling back in there with a jumper cable to make sure it's not the starter (or IS the starter) makes good sense.

Assuming your engines are identical you can plan out what needs to get connected where, and even try it out, on your port engine before you or your mechanic crawl back in there.

[seasalt]

I am leaving tomorrow for a two week cruise to Elbonia. I will leave a note for the mechanic that reads "boat won't start".

In other words I have gotten over my pay grade trying to figure this out so I am leaving town.

[seasalt]

The mechanic came today and confirmed the electrician's diagnosos. Good voltage in start circuit and that the Bendix was engaging the flywheel but not turning it.

While I pushed the start button he hit the starter with his ball-peen hammer and the engine started.

He got back there with no problem, except for the cramp in his leg. Much cursing.

His comments were that the starter did not look very old (non Cummins brand) and that it was the cleanest back side of an engine room that he had ever seen on a older boat. Thanks Chuck.

New Cummins starter with a one year warranty is on the way.

[DougSea]

Glad you got that resolved! (Or at least identified!)

Do they like boats in Elbonia? Isn't it mostly covered in water a few feet deep?

[seasalt]

Yes and lots of mud.

[Serenity]

Would it be possible to jump the terminals on the neutral safety swich, put tranny in neutral and try to start

[seasalt]

Did that. I jumped around the NSS.

Everything in the circuit was fine. The starter was engaging the flywheel but not spinning the engine.