Prop shaft bonding (yanmar 1gm10)

[fjweaver]

Have removed and replaced prop shaft to replace cutlass bearing. Replaced hull and shaft anodes. Bonding between hull anode and p-bracket is fine but seem to have lost bonding to prop shaft. There's a connection between the shaft and the coupling but nothing from engine block. I can't see what would have changed as I've always had the prop shaft connected to everything else. Any ideas please?

 

[VicS]

If the hull anode is to protect the prop then there must be either an " Electroeliminator", or similar, making direct contact with the shaft or a connection to the engine or gearbox and a bridge across the two halves of the flexible coupling.
( A belt a braces policy to connect a hull anode to the shaft as well as having a shaft anode but no reason not to especially as the connection through the oil filled gearbox bearings can be poor )

Check the bonding connection to the engine/gearbox and the bridge across the coupling

Why is the P bracket connected to the anode. If its bronze it is not necessary and in fact should not the connected to the same anode as the stern gear.

 

[pvb]

If you have a shaft anode, what's your concern?

 

[Tranona]

Agree. You really don't need a hull anode at all. Th P bracket does not need an anode and the shaft anode will give far better protection as it is closer to the prop and a much stronger direct connection to the shaft.

Hull anodes tend to get fitted out of habit without thinking through what needs protecting and how best to do it. BTW the make and type of engine is irrelevant, although as you probably know the 1GM has its own anode in the cooling water circuit, located just above the starter motor.