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Old 04-08-2017, 10:35 PM   #1
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Mystery Part on a Yanmar 6lypa-STP

I have twin 2005 Yanmar 6LYPA-STP 370HP diesel engines. We purchased this mostly fresh water boat last year from the original owner.

On the port side of the starboard engine, directly aft of the coolant reservoir, there appears to be a sensor or unknown part.

Here is a pic of the part: http://i258.photobucket.com/albums/h...ery%20Part.jpg

There are two large gage wires and two smaller wires attaching to this part. On the starboard engine, the large gage wire that is aft is heavily corroded, as is the nut that connects this to the part.

You can see the pic here: http://i258.photobucket.com/albums/h...Close%20Up.jpg

On the port engine, the wire, nut and stud is pristine.

I will need to replace the heavy gage wire by snipping the corroded wire down to the good wire and extending it (a lead) to the part with new hardware. There is not a lot of wire to work with as it goes into a wire case and harness.

Does anyone know what this part is and what it does?

Any ideas of connecting a replacement lead to the heavy gage wire?


Thanks,

JimL
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Old 04-08-2017, 11:01 PM   #2
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I believe those are starter relays. My 4JH3's have the same, mounted near the starter. I think they solve a voltage drop problem in the long wire run to the flybridge.

Rafe
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Old 04-08-2017, 11:53 PM   #3
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It is a magnetic switch for the starter. I just changed a similar one on my Cummins.
If the large wire is burned the magnetic switch is probably degraded as well. Change the magnetic switch and clean up or cut back the wire to a good contact. If you are worried about a short wire you need to know that the large wires don't care which post they are attached to. The small wires from the ignition switch excite a magnetic coil to make the contact. They need to go back where they are proper polarity so mark left and right as you remove them.
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Old 04-10-2017, 09:55 PM   #4
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Thanks for the tips. I inspected the boat again over the weekend based on your comments. I did see evidence of heat damage as the corroded wire meets the relay.

When I followed the two small wires, I saw that they connect to a plug as part of the wire harness. I need to find the correct relay with the correct plug connector.

My first step is to locate a dealer that sells the relay. When I unbolted the relay, I could not locate a part number.

Do you have any idea where I can secure one?

Thanks,

Jim
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Old 04-10-2017, 10:21 PM   #5
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You need to go to your Yanmar dealer for the exact part. In a pinch you could use a Cummins or Ford diesel magnetic switch as long as it is marine with two large and two small wire exciter. The automotive ones are 3 wire with the small single wire and using the block for a ground instead of the second wire.
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Old 07-24-2017, 09:29 PM   #6
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This mystery part on the Yanmar is actually the glow plug heater relay, not the starter relay. Once I identified the correct part which took some time on the phone with the parts dealer, it fit like a glove.

Thanks for your advice.

Jim
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