Dear Boat Doctor,

I have a Yanmar 4JH2DTE engine on my boat. The engine runs great but I have a hard time starting it. Sometimes when I turn the key nothing happens, but if I try a few more times it starts fine. What's going on?

David Clark

Poway, California

Dear David,

This is a well-known problem with Yanmars. Over time, the key switch and connectors in the wiring harness can develop just enough resistance to not reliably pull in the solenoid and engage the starter.

There are three ways to fix this: you can go after the resistance in the connectors, install a new wire from the key switch to the solenoid or add a slave solenoid.

If you choose to clean up the connectors you'll need to trace the harness back to the switch from the engine, cleaning each connector and making sure it is making good contact. I would add a little dielectric grease to each one to assure it stays clean.

Replacing the wire with a continuous 12-gauge wire is an option, but a little bit of a hassle to route. I'd leave the old wire in the harness and just tape off the ends.

I think the best solution is add a slave solenoid in the engine compartment. The idea is to have the key switch operate the solenoid and then the solenoid contacts will pull in the starter. A simple automotive solenoid will work fine, like the Cole-Hersee SKU594242 available from West Marine.

You will need to mount the solenoid somewhere in the engine compartment. Run a No. 8 wire from the starter post to a large terminal on the solenoid, and another No. 8 from the other post to the start terminal on the starter solenoid. Attach the wire from the key switch to the small terminal on the solenoid and the other post to engine ground.

The key switch will operate the new solenoid just fine and the solenoid will operate the starter solenoid. As an added bonus, you can add another start switch in the engine compartment- just connect it in parallel with the key switch-the extra switch is great when working on the engine.