Position of anode on propshaft?

[capetown]

I want to fit an anode on the propshaft between the p bracket and hull exit.

Looked at other boats in the yard but there doesn't seen to be any pattern.

Me thinks that closer to the p bracket woud be better than halfway, because when it's eaten away, it might unbalance the shaft?

But on the other hand, if it's close to the bracket there's a big lump to snag weed/ropes.

Oh, decisions decisions.

 

[Tranona]

Assume this is on a boat other than a Pageant. The shaft anode does not protect the P bracket, but the shaft and prop. It is normal to fit them as close to the prop as possible - ie just in front of the P bracket. If you get the correct size anode and fit it correctly it should not move or cause any balance probelms.

ps why do you think you need an anode. Does the boat have one already?

 

[VicS]

ps why do you think you need an anode. Does the boat have one already?

Or is there some galvanic corrosion of the stern gear that has to be halted?

 

[vyv_cox]

Position becomes even more important if the shaft diameter is small, e.g. 3/4 inch. The natural frequency of the shaft will then be lower, with an increased tendency for resonance if the anode is central on the shaft. Having it as close as possible to the P-bracket, consistent with water flow through the cutless bearing, will reduce this tendency.

 

[capetown]

You are quite correct it's not for my 1979 Westerly Pageant, soon to be for sale, with the wooden interior

It's for my "new" Hunter 265.

The boat has a single bolt anode, and there is some prop corrosion.

There's a cct from the anode to the p bracket (in boat wire), but not to the shaft/prop. no doubt because of the rubber cutlas brg.

The other thing I noticed in my lookee around, those that had shaft anodes, had a lack of fouling.

I wonder why?

 

[VicS]

You are quite correct it's not for my 1979 Westerly Pageant, soon to be for sale, with the wooden interior

It's for my "new" Hunter 265.

The boat has a single bolt anode, and there is some prop corrosion.

There's a cct from the anode to the p bracket (in boat wire), but not to the shaft/prop. no doubt because of the rubber cutlas brg.

The other thing I noticed in my lookee around, those that had shaft anodes, had a lack of fouling.

I wonder why?

An anode connected only to the P bracket will only be protecting the P bracket.

To protect the prop a shaft anode is the obvious choice although a hull anode could be connected to the prop via a connection to the gearbox casing and a bridging cable across the flexible coupling. The connection via the gearbox may or may not be successful. Connection via brushes running on the shaft inboard of the stern-gland is an alternative. Eg using MG Duff's "Electro-eliminator". q.v.