Shaft brush

[lydiamight]

I'm trying to source a shaft brush, sometimes called a shaft wiper. My propshaft and prop are electrically isolated from the engine and I need to fit a "brush" onto the shaft, just behind the gearbox, which I can then wire to an anode. I,ve tried fitting a shaft anode but never seem to get them to stay on. This year the electrolysis is going to cost me a new prop so all help would be appreciated.

 

[DavidGrieves]

Hi

Try here http://www.asap-supplies.com/

Follow link for

Miscellaneous & Stern Gear
then
Anodes & Cathodic Protection

David

 

[tugboat]

I'm not familiar with Dehlers so don't know your setup. If the electrical isolation of the shaft is because of a rubber coupling, could you not just fit a bonding wire across the coupling? Lots of boats have that and it seems to work OK.

 

[nedmin]

you can have a wire bridge across the coupling, but still not have good continuity from propshaft to boat earth due to oil being on the g/box bearings, just fitted a brush on the outer rim of the coupling as I was getting stray currents. Got a brush holder from an electric drill made a bracket out of brass,then you need an old starter brush (because they have a high copper content in the carbon brush for continuity) you could get one from a scrap yard.saw the brush to fit the brush holder you need a phosphur bronze spring to provide tension.run a wire from your brush to your earth point.

 

[lydiamight]

Thanks everyone for all of your help. The engine/gearbox is electrically isolated from the shaft by a composite coupling--there is no point in bridging this gap as the engine /gearbox itself is not connected to any anode. There being no need to with this particular setup. ASAP Supplies have what looks like exactly the right bit of kit. I shall try one and see how I get on.

 

[qetoo]

I too lost a prop to electrolysis before I installed a brush on the shaft, but haven't had a problem since then. However, I still keep two zinc anodes on the shaft. The brush is wired to the anode plate bolted to the stern. The brush assembly is about a 0.25 metre spring metal leaf holding the brush against the shaft. I got it at a marine dealer.

The electrolysis to the prop was rather interesting. It ate stress cracks at the hub of each blade and the entire prop had turned red.