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BarryL 07-21-2012 05:06 PM

Yanmar and No Start

The boat I race on has an older yanmar engine. I don't know the model, but it makes around 14 HP. Anyway, I've been racing on this boat for a few years and the engine is easiest starting diesel I've ever seen. The owner turns the key, presses the start button and the engine starts in 1 second.

This year the owner reported that the engine would not start. He would press the start button and nothing happened. He did some troubleshooting and determined the starter was bad. I assisted him and we were not able to get the engine to turn over. So I removed the starter (which wasn't too hard to do) and he bought a rebuild. We put it in this past Monday and the engine started right up. He raced that night. We had race practice Tuesday, and raced Thursday. The engine started and ran great. Thursday night, after the racing was over, the engine would not turn over. We sailed back to the mooring.

Friday I helped trouble shoot. The batteries were a little low (12.4V) so I tried my jump pack. No go. Then I removed one of my new group 27 batteries from my boat and connected that. No go. We gave up and I went home.

Today we tried again: perhaps the rebuilt starter was no good. I removed it and we powered it up sitting on the cabin sole. It spun nicely when I applied power to the main terminal and solenoid. I put the starter back in and nothing. I checked power at the solenoid and when the start switch was activated I saw 12.3V at the solenoid. I measured power at the starter on the heavy wire from the battery and also saw 12.3V. The power was a little low, but I thought it would be enough to turn the engine over.

At this point I have exhausted my knowledge so we went home. The owner got a mechanic to look at the boat and he had it running in about 15 minutes.

Anyone care to guess at the cause?

I'll put the solution to the problem in the next post.


BarryL 07-21-2012 05:11 PM


The mechanic reported that the main battery ground, the one connected to the engine, was corroded and bad. He removed the connections, cleaned, and re-installed. Presto chango, the engine starts right up.

I was fooled because I was able to see voltage. I have no way of measuring current, so this one got me.

In the future I will be a lot more careful about checking ground connections.


lajimo 07-21-2012 07:51 PM

Yanmar and No Start
Great follow up, thanks for the info.

CalebD 07-21-2012 11:11 PM

Re: Yanmar and No Start
Similar diagnosis but different problem.

I was checking out a friends boat whose electrical system was not working properly (no running lights, cabin lights and several other switches on the main board did not function).
It was not the first thing I checked but I opened up the battery locker to have a look. The fittings on the battery terminals did not look great but seemed ok. I noticed that one wire was not connected to the 2nd battery's neg (-) terminal. Apparently that wire supplied the ground to one of the negative buses so nothing attached to that bus worked until we shined up the connector and attached it to the battery.

JimsCAL 07-22-2012 08:16 AM

Re: Yanmar and No Start
Thanks for the update. Good reminder that one of the first things to do when you have such problems is to clean all the battery connections.

One bit of information to other Yanmar owners is that they are noted for having a starting problem if the cable run from the engine to the panel is too long. Voltage drop to the solenoid can cause an intermittent no-start issue. The solution is to add a starting relay in the circuit. Any Yanmar dealer can help with details.

dabnis 07-22-2012 09:21 AM

Re: Yanmar and No Start
As you now know, you might see a "surface' reading on your meter but with so much resistance in a bad connection and trying to pull a heavy load through it, no go. A similar condition can exist when grounding a spark plug outside an engine to check for spark. If the high tension voltage is marginal you might see spark but when you put it back in the engine the compression adds more resistance and the plug won't fire.

Paul T

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