Bonding and anodes

[chris-s]

This is our first season with a boat that has hull, engine and prop anodes. I posted back in August how I was surprised to find the prop anode had completely wasted after four months. I fitted a new one at the beginning of September.

So, the boat had new hull and prop anode fitted this season and the pencil anode in the VP 2003 was good enough that you could still make out the lettering cast into it, tho I don’t know how old it actually was. The previous owner also had a new prop fitted whilst shore last night winter, presumably the previous one had de-zinc’d but we never saw it.

The boat is kept on a swing mooring and this year has only spent four or five nights in a marina but never connected to shore power.

The hull anode is about eight feet from the prop and is only connected to a keel bolt, there are no other connections to any other keel bolts.

I removed the engine anode plug to flush the engine when she came ashore the other week only to find no anode left, well, barely a trace.

The replacement prop anode was already beginning to noticeably degrade after being fitted for four weeks (see photo).

No thru-hulls have any bonding and there is good electrical connection from engine to prop shaft.

Whilst ashore this winter, is there anything I should do/check or is this expected?






Chris

 

[VicS]

If the hull anode is 8ft from the prop it is probably too far away to be very effective.

If it is only bonded to a keel bolt it will be offering no protection whatsoever to the prop.

Prop anodes do erode fairly quickly due to being fairly small and in contact with a copper alloy item with a relatively large surface area ... viz the prop.

A hull anode much closer to the prop and with electrical bonding to the prop via the engine and gearbox might help a little but in any case will serve as back up if the prop anode is totally consumed or lost.
A shaft anode would be better if one can be fitted. I see that it isn't.

The engine anode is a separate issue. It protects only the engine cooling system. Replace it.

You could use the exiting hull anode as a grounding point, ie contact with the water, for the shorepower earth, especially if it is at present grounded via the engine and stern gear.

.

 

[Tranona]

8 feet is a rather long way away but if it is bonded to the shaft through the gearbox it should have some effect. You may need a strap across the coupling if it is a flexible type. I have just installed an anode for the prop and it is about 1m away in direct line of sight to the prop and bonded to the shaft by brushes that run on the shaft. Although that current anode is doing something it realy is not necessary for the keel and it may be worth fitting another node specifically for the prop but closer.

 

[vyv_cox]

My prop anode lasted one season, shaft anode lasted two. I then painted the prop with Hammerite/Velox. Prop anode now lasts two seasons, shaft anode more than four

 

[chris-s]

My prop anode lasted one season, shaft anode lasted two. I then painted the prop with Hammerite/Velox. Prop anode now lasts two seasons, shaft anode more than four

I used the same paint combinations and it has faired very well.

Thanks for the replies guys.