Starter problems Yanmar 3GM30

Benny17441 · Jul 16, 2017

Old wiring (10+ years) induces voltage drop to solenoid. It likely has nothing to do with the engine being warm but what is going around when the engine is warm; batteries in discharge mode, hot wiring. A good cleaning, brushes replacement and bench testing of the starter itself will be money well spent. The solutions for the voltage drop malady are the addition of an auxiliary solenoid, replacement of wiring harness and push connectors or the rewiring of an external circuit to solenoid. Some have moved the push button starter switch to near the engine compartment or added an adittional one.

cymeyer · Jul 16, 2017

Ilanortho said:
Hi;

Am experiencing frequent intermittent starting problems when the engine is warmed up. Usually out on the water it takes several (2-3) turns of the key before the starter will kick in. New cockpit instrument panel was installed two years ago with new switch, but this preceded it. Batteries new and always charged.

Is it something to do with the starter itself/ solenoid? All terminals are clean and corrosion free and tight.
Thanks. Ilan

Ilanortho,
We have a Beneteau 321 with the same engine and had the same issue about 15 years ago. I even replaced the starter solenoid and that was not the issue. As you will find in other posts, it is a poor wiring harness with connectors that corrode. With the help of a friend who had the same boat, we ran a solid wire from the starter button to the starter solenoid. Never had the problem again since.

Bill Roosa · Jul 16, 2017

Hunter in its wisdom put something like 13 connections between the battery + , start switch, solenoid, starter, ground circuit, battery - and each one has a small voltage drop. Many use an additional solenoid but that is just treating the symptoms (IMHO). Better to neuter the engine harness of ALL its quick connect plugs or run a dedicated wire from starter switch to solenoid. As a quick fix try taking all the engine harness quick connect plugs apart and after inspecting for corrosion, put it back together again.
An additional advantage to neutering the engine harness is that the instruments read properly. My engine temp always read hotter than I knew it was till I fix the wiring, the tack settled down also.

Roadking Larry · Jul 16, 2017

As others have said the 1st thing to do before replacing expensive parts is to clean all your electrical connections related to the starter circuit.

heritage · Jul 16, 2017

There is a condition called "heat soak" that occurs when a starter and solenoid get hot. This creates more resistance in the starter and solenoids wiring thus requiring more amperage from the battery to do their job. This is likely why you are only having problems when the engine is hot. Sooner or later though, you will probably have starting problems when the engine is cold.

DStegs49 · Jul 16, 2017

Similar problem. Same PITA. Mine starts every time at the dock but after about 5 hours of sailing (with a cooled engine), it doesn't start. Usually when I am either in or approaching the channel to Muskegon Lake. I let my wife take it and I go below. No not to let her have the problem but to jump between the hot post of the starter and the solenoid on the starter with a screwdriver. It miraculously starts effortlessly when I do this. Next on my to do list is (as mentioned before) run a dedicated, solid wire from the starter button to the post on the solenoid. Connectors are good, until they ain't. Try this with your HOT engine and see if you get the same results I do with a cold engine.

Rob2435 · Jul 16, 2017

i had the same problems years ago, listened to all the suggestions on this site and nothing worked. I ran a 10awg wire to replace the 12awg and haven't had a problem since.

skunther · Apr 30, 2025

I’m noticing the same issue. I’m measuring 10v at the solenoid when cranking the engine. This should be 12 V, correct? So I am losing 2V somewhere between the start button and the solenoid?

Foswick · Apr 30, 2025

That's a big voltage drop, in particular because your battery is probably > 12V. I would be surprised if simply installing a larger wire would fix that. I would just keep testing the voltage, starting at the solenoid and working backward toward the battery until you find out where the drop is actually occurring.

I am very curious.

skunther · Apr 30, 2025

Where would I check next? The only other obvious place is at the starter switch. The wire runs into unknown recesses of the boat between those two points.

Foswick · Apr 30, 2025

Well, one easy thing you can do is test right at the battery. If the voltage drops under load, at the battery - there's your problem.

It doesn't take much further before I am out of my depth and would call my friend that actually knows about these things.

leo310 · Apr 30, 2025

Look at your wires to the starter from the battery. the switch is only for the solenoid. Had a problem turn out bad ground wire.

marcham · Apr 30, 2025

The yanmar wiring harness is notorious for getting microbreaks and becoming brittle once it gets to 25-30 years old.... Time to remove it and pull new wires for the engine (12V power, ignition, start signal, oil px, coolant temp, etc....). Takes about a day on most boats. Suggest using marine grade tinned instead of the copper Yanmar used. The materials will cost you about half of what they sell the harnesses for (if you know how to do proper sealed marine crimps). If you're paying someone to do it, it would likely be cheaper to just buy the new harnesses (one for the engine, one extension to the controls. Just did this on a 3GM30F.