Mystery diode on alternator

[Lift12]

Hello,

New to me 1998 7.4 MPI Bravo 1 (0L347054) twins. I believe the alternators are Mando, but I've been wrong before.

I've discovered a fuse holder dangling from each alternator, completely unsecured excpt by the ring terminal. 20A MDL type fuse inside, intact. It is just a tail, only one wire connects to it. I removed them for a closed look. Cutting off the heat shrink revealed a diode inline to the fuse.
I can find no mention of this part in the Merc manual 23 or parts listing.

I admit I know very little about alternators with excitation circuits.

What is the purpose of this part?
Is it a factory part? It appears it could be by the build quality.
And the real question, if I should re install it, which terminal does it go on...? I should have taken a photo but didn't...

Thanks.

 

[dubs283]

It's possible someone ran an isolater at one time and it's now abated. Could have been part of that system. Were they on the output stud?

If you can, post a pic with the leads as you found them

 

[Lift12]

This is the device. I wish I could show you how it was connected. I too thought it was some remnant of previous device and so I removed it without documenting exactly which stud it was on. Now that I've found the diode inline I worry that it is indeed a necessity.

 

[dubs283]

If it wasn't attached to anything on the other end then no worries, probably a remnant of what I could only guess was an isolater. By the looks of the ring terminal it appears 1/4" and would have been on the output terminal/stud.

If they are/were attached trace the wire and you'll find the system.

 

[76SeaRay]

Electric circuits require two wires to do anything. Unless there was a wire in the cap of the fuse holder or attached to the tab on the side of the fuse holder (most likely) that went somewhere, this doesn't do anything.

 

[Lift12]

Thank you. I agree that it takes two leads to make a circuit, which made these even more mysterious. The tabs for that second connection had been removed. I ran the boat today without them with no issues.