Mysterious black box Yanmar 3GM30

[FaberCastell]

Hello!

I have this black box connected to the cables running from the engine to the control panel and wonder if someone knows what it is? It is completly closed and there is no way of opening it. The surface is like rubber and it has four cables (black, blue, red/black, yellow/green) running into it. I can find some but not all of the cables on the wiring diagram. It could be some kind of charging regulator but it has no heatsink like the one I have seen when I googled. According to the diagram it is also supposed to be a fuse box somewhere on the main cables but I have not found one. Could it be something in connection to that?

 

[rudolph_hart]

Another possibility to consider is that it is a Relay for the starter.

I have a 30GM30F, and it has a similar black box mounted above the bell housing. It looks factory (Dehler) fitted. Yanmars are known to have occasional starter/solenoid problems, and fitting a relay is a known preventive measure.

Hope this helps.

 

[FaberCastell]

Yes could be a relay. The electrical system is down for rewiring but when I get it up and running I could listen if it makes any sound aswell. But the yanmar relays I see when I google does not like like this black box. And should not the cables be heavier in that case?

I am not going to throw it out (like I have with a lot of other stuff during the rewiring) but it would be good to know how all the stuff works.

 

[VicS]

Yes could be a relay. The electrical system is down for rewiring but when I get it up and running I could listen if it makes any sound aswell. But the yanmar relays I see when I google does not like like this black box. And should not the cables be heavier in that case?

I am not going to throw it out (like I have with a lot of other stuff during the rewiring) but it would be good to know how all the stuff works.

Not a relay carrying starter motor current but possibly a relay between the starter button and the starter solenoid therefore just carrying the current for the solenoid coil. Some engines have such a relay although nothing shown is in the wiring diagram you posted.

would not expect one to be permanently wired in though as this item appears to be

 

[FaberCastell]

According to a Yanmar specialist here in Stockholm the black box is an amplifier to the water sensor down at the gear box. Sounds reasonable so I guess the case is closed.