Yanmar 4LH ignition switch

[willyritch]

We just picked up a new boat with a Yanmar 4LH with about 3800 hrs on it. After the engine has been running for awhile (>30 mins??) and I shut it down it will not restart. There is a relay just upstream of the solenoid and when the key is turned to start, a white wire delivers 12v (+) to the relay, which in turn delivers 12v to the solenoid. I tried changing the relay but that wasn't the problem. When everything is working correctly, I can see 12v (+) at the relay, but when it's not, that white wire is only delivering 1.5v (+).

There are two helm stations--two Yanmar control panels. Each control panel has a harness that is divided into three bundles of wires--three connectors attaching the harness to the engine. If I temporarily disconnect any one of those three connectors, the engine will start. Even after I reconnect the harness, the engine still starts. All is right with the world until I run the engine for a little while.

The boat also has Vetus electronic shifters--one set at each helm station. When I disconnect any of those harness connectors the shifters are also disabled.

One work around is a momentary switch that delivers 12v (+) to the relay to crank the engine...that works in a pinch. But I want to find the root of the problem.

Any ideas?

[s/v Jedi]

Originally Posted by willyritch

We just picked up a new boat with a Yanmar 4LH with about 3800 hrs on it. After the engine has been running for awhile (>30 mins??) and I shut it down it will not restart. There is a relay just upstream of the solenoid and when the key is turned to start, a white wire delivers 12v (+) to the relay, which in turn delivers 12v to the solenoid. I tried changing the relay but that wasn't the problem. When everything is working correctly, I can see 12v (+) at the relay, but when it's not, that white wire is only delivering 1.5v (+).

There are two helm stations--two Yanmar control panels. Each control panel has a harness that is divided into three bundles of wires--three connectors attaching the harness to the engine. If I temporarily disconnect any one of those three connectors, the engine will start. Even after I reconnect the harness, the engine still starts. All is right with the world until I run the engine for a little while.

The boat also has Vetus electronic shifters--one set at each helm station. When I disconnect any of those harness connectors the shifters are also disabled.

One work around is a momentary switch that delivers 12v (+) to the relay to crank the engine...that works in a pinch. But I want to find the root of the problem.

Any ideas?

99% sure you have a bad ground. You traced the positive wires to relay and solenoid… repeat for the negative. Start with confirming the engine block has a solid connection to DC negative, then trace the negative wires in the wiring harnesses and how they connect to the engine block.

[willyritch]

That seems like a reasonable thing to check. My oil pressure gauge was acting a little wonky (a manual gauge confirmed the problem isn't the actual oil pressure) and that could also point to a bad ground. I'll chase down that theory. Run it to ground, so to speak.

[bil56]

prob bad ground ...
on a boat, the main problem is the many connectic,
exchange your beer can for a spray of contact cleaner !