Shaft anode? Macwester 27

[ronmarson]

When I was cleaning the prop I found a large crack so set about trying to get it mended. The engineering types all said it could not be done, partly because the prop was 'Pink' from de zinkyfacation. (the spell checker doesn't like that)
So I have found a second-hand prop to fit and don't want the same problems.
So my question is, should I fit a shaft anode?
I have a hull anode fitted about 4 ft. from the prop. It seems to be working as it should. ie. It looks like it has been nibbled by a sea monster, but it is not helping the prop.
Macwester 27 1976 vintage.
Capt. RoN

 

[Nicholas123]

I don't have any other anode but my prop anode Ron & my prop looked pristine.Maybe my keels about to fall off
What is your anode connected up to?

 

[Appledore]

Happy Easter Capt'n Ron,

My Mac Rowan has one MG Duff pear-shaped anode under the hull, which is connected by one wire to the prop shaft and another to the engine block (negative earth) one wire from each of the 2 bolts. This was there 15 years ago (although I've replaced the anode a couple of times), and there has been no sign of de-zincification (checker didn't like that one either!!), on the old prop, or the 3 year-old one, which rings like a bell. And certainly on my Rowan, there's no room to fit a shaft anode.
The anode is not working unless it's 'nibbled' as you put it!

Geoff

 

[vyv_cox]

I prefer a shaft anode if it is possible to fit one, simply because the electrical path is shorter and simpler. On my Sadler I only have a shaft anode and the propeller's own anode (Bruntons Autoprop). The P-bracket and the prop are painted, which limits the amount of corrosion that can take place.

 

[VicS]

When I was cleaning the prop I found a large crack so set about trying to get it mended. The engineering types all said it could not be done, partly because the prop was 'Pink' from de zinkyfacation. (the spell checker doesn't like that)
So I have found a second-hand prop to fit and don't want the same problems.
So my question is, should I fit a shaft anode?
I have a hull anode fitted about 4 ft. from the prop. It seems to be working as it should. ie. It looks like it has been nibbled by a sea monster, but it is not helping the prop.
Macwester 27 1976 vintage.
Capt. RoN

4 ft a bit more than ideal perhaps, but have you checked the continuity of the bonding between the anode and the prop?

A good manganese bronze prop should not suffer from dezincification ( my spell checker is happy with that!) unless there is some cause but if you can and fancy fitting a shaft anode then there is no reason not to do so

My Mac Rowan has one MG Duff pear-shaped anode under the hull, which is connected by one wire to the prop shaft and another to the engine block (negative earth) one wire from each of the 2 bolts.
The anode is not working unless it's 'nibbled' as you put it!

Geoff

How do you manage to connect a wire effectively to the prop shaft?

 

[Appledore]

How do you manage to connect a wire effectively to the prop shaft?

Errm, not the actual shaft itself, of course but the outer sleeve. The connection was 'always there', so I've no idea if it is effective. Probably wouldn't be, thinking about it, as the shaft runs within 2 bearings!

 

[vyv_cox]

Errm, not the actual shaft itself, of course but the outer sleeve. The connection was 'always there', so I've no idea if it is effective. Probably wouldn't be, thinking about it, as the shaft runs within 2 bearings!

Sounds like its intention is to protect the stern tube rather than the prop and shaft. Many stern tubes are made from brass as bronze tubing is not easy to source. They can suffer from dezincification, example on the website.

 

[Tranona]

Errm, not the actual shaft itself, of course but the outer sleeve. The connection was 'always there', so I've no idea if it is effective. Probably wouldn't be, thinking about it, as the shaft runs within 2 bearings!

The wire to the engine block is to connect to the shaft through the gearbox and coupling. The one to the stern tube is just for the tube.

 

[Appledore]

Thanks, makes complete sense.

 

[rob2]

There can be a problem with the bonding from the engine block, through the gearbox and coupling (many of which have a rubber plate). It would be a good idea to check the continuity from the anode to the propellor - a multimeter should only show a couple of ohms, although it can be difficult to get a good contact with the probe on the anode. If there is a problem, then it may be possible to bridge from the engine block to the gearbox casing (less than ideal due to bearings) and to bridge the coupling with a braid from one side to the other. If that is unsuccessful, then a brush on a leaf spring can be rigged directly onto the shaft (like a brush in an electric motor).

Rob.