Mystery with Renault Couach RC8D gearbox – spinning stud/nut

[Hubiert]

Hey. I hope you can help solve a mystery.
I have recently renovated a Renault Couach RC8D engine. But after installing it in my boat, I realized a nut on a stud was rotating on the back of the gearbox. I strongly believe this is not intended...

The stud/nut is rotating freely and can move 2-4 mm back and forth. When the engine is running, it rotates, but it can be stopped with your fingers. The gearbox still works fine and goes in and out of gear.

I have attached a photo was not able to ad a vide unfortunately

I hope someone here knows something, as I am afraid I'll have to take the gearbox out and dismantle it to find the problem

 

[jamie N]

I used to have one of these fantastic little engines. I've looked back at a video from my engine, which does show 'this' nut, and nothing is moving. However, I reckon that there's nothing to worry, about as I believe that it's irrelevant to the engine itself, and most likely an earth or continuity attachment point, or some such thing, possibly for a different version.
Like you, if it was on my engine I'd worry about it, but the engine runs fine, the g/box does everything that it's told to do, and I guess that the oil's not contaminated, so it's probably not a fault, thus an "negative electrical continuity bonding point" (NECBP) would fit the bill.
I'd be very wary of stripping down a gearbox, where spares aren't necessarily readily found, to fix an issue that hasn't occurred.
At the moment it's a curiosity, I'd absolutely avoid making it a fault.

 

[Hubiert]

Thanks.
I finnaly found and exploded wiew of the gearbox.

And will be able to fix it from the outside.

Just ned to pull it back and fix I so I doesn't rotate

 

[DownWest]

The engine is a marinized Hatz diesel. Common in site kit like cement mixers. BMW also did a version for boats.
The Renault version suffered a bit from problems with the alternator, which was incorperated within the flywheel casing.
Some were converted with a small belt drive alterator in a more conventional set up.

 

[penberth3]

The engine is a marinized Hatz diesel. Common in site kit like cement mixers. BMW also did a version for boats.
The Renault version suffered a bit from problems with the alternator, which was incorperated within the flywheel casing.
Some were converted with a small belt drive alterator in a more conventional set up.

Is any of that relevant to the OP's question?

 

[DownWest]

Is any of that relevant to the OP's question?

Bit of background, which might help later, esp with the alt.

Not to mention sources of spares?