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Anode needed on inside shaft?

Jul 7, 2016
62
Hughes Columbia 8.7 Collingwood
I see that an anode on my shaft close to my stuffing box had fallen off. The anode had no noticeable deterioration (I don’t know how old it is). It is missing a bolt which attaches the two parts of the anode to the shaft... so I assume that the bolt had come loose and the anode fell off. Initially I planned to replace it but then thought...is an anode on the shaft located inside the boat where it will (hopefully) never be submerged, needed? Does it provide any protection at all? Should I replace it?
 
Jan 11, 2014
6,566
Sabre 362 113 Fair Haven, NY
An anode placed on the interior section of your shaft will prevent the shaft from falling out of your boat if it separates from the transmission coupling.
Yep, this is why. A hose clamp could also be used or a SS shaft collar. Folks who have PYI dripless shafts often put them on to back up the shaft seal in case the seal comes loose. In the medical world, using an anode for this purpose would be an "Off Label" use.
 
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Jan 11, 2014
6,566
Sabre 362 113 Fair Haven, NY
I could envision some shaft unbalance.
Why? Other than the obvious, what is the difference between mounting an anode inside the boat or outside? How would an anode mounted inside the boat cause the shaft to be unbalanced but when mounted outside it doesn't. The shaft is typically supported in 3 places, the strut, stuffing box, and transmission.
 
May 29, 2018
228
Canel 25 foot Shoigama, japan
Hi Suncatcher
This is how I see your situation.

1. I see that an anode on my shaft close to my stuffing box had fallen off.
By this do you mean that the anode is actually fitted inside the boat? If so very unique!

2.The anode had no noticeable deterioration (I don’t know how old it is).
If it is fitted on the inside of the boat with no contact to water, you can expect it to last for ever, no matter how old it is.

3. It is missing a bolt which attaches the two parts of the anode to the shaft... so I assume that the bolt had come loose and the anode fell off.
Yes. if it is missing a bolt that is very likely the cause of it falling off.

4. Initially I planned to replace it but then thought...is an anode on the shaft located inside the boat where it will (hopefully) never be submerged, needed?
I too hope it will never be submerged there, So, no. Realistically it is not needed, But.....

5. Does it provide any protection at all?
It provides ZERO electrolytic protection. However, as mentioned by Ted, something fitted to the shaft would stop it propelling out of the tube if the coupling ever gave way.

6. Should I replace it?
Your post has taught us all a new trick. If you have a spare shaft anode you should fit it internally, near the stern tube. That way you will know where it is and in the event of a coupling failure it will keep the prop shaft inside the boat and reasonably safe.

Great idea!

So, get a new bolt and refit as specified.

gary

 
Feb 8, 2014
1,251
Columbia 36 Muskegon
I once rescued an old Chris Craft runabout whose shaft pulled out. Didn't fall all the way out so they weren't sinking, but not enough exposed to pull it back in. A hose clamp would have been just as good, that's what I use.
 
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Jan 22, 2008
7,892
Beneteau 323 Annapolis MD
Why? Other than the obvious, what is the difference between mounting an anode inside the boat or outside? How would an anode mounted inside the boat cause the shaft to be unbalanced but when mounted outside it doesn't. The shaft is typically supported in 3 places, the strut, stuffing box, and transmission.
AT EASE, PLEASE, dlockner. I was not comparing inside to outside. It was just the effect of the zinc itself. I have handled many a zinc, and they are not precision cast, in my eye. I wonder if anyone has ever done a balance test of a few of them? I'm here in Annapolis in the middle of a hurricane at the moment. Getting alot of quick power hits, and the router drops off/OOS.
 
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Jul 7, 2016
62
Hughes Columbia 8.7 Collingwood
I once rescued an old Chris Craft runabout whose shaft pulled out. Didn't fall all the way out so they weren't sinking, but not enough exposed to pull it back in. A hose clamp would have been just as good, that's what I use.
Would the hose clamp, being asymmetrical, unbalance the shaft? If not, easy cheap fix.
 
Feb 2, 2006
452
Hunter Legend 35 Kingston
Maybe a picture of the "inside anode" would be helpful. Maybe it "is" a SS retaining collar. They do make "collar" anodes that look similar to the retaining collar. The nature of the metals surface or other markings would be a clue to which it is.
 
Jul 7, 2016
62
Hughes Columbia 8.7 Collingwood
I once rescued an old Chris Craft runabout whose shaft pulled out. Didn't fall all the way out so they weren't sinking, but not enough exposed to pull it back in. A hose clamp would have been just as good, that's what I use.
Would the hose clamp, being asymmetrical, be enough to unbalance the shaft?
 
Jul 7, 2016
62
Hughes Columbia 8.7 Collingwood
Maybe a picture of the "inside anode" would be helpful. Maybe it "is" a SS retaining collar. They do make "collar" anodes that look similar to the retaining collar. The nature of the metals surface or other markings would be a clue to which it is.
It’s definitely and anode.
Maybe a picture of the "inside anode" would be helpful. Maybe it "is" a SS retaining collar. They do make "collar" anodes that look similar to the retaining collar. The nature of the metals surface or other markings would be a clue to which it is.
It’s definitely an anode, like in this pic...
1596553664021.jpeg
 
Jan 27, 2008
2,967
ODay 35 Beaufort, NC
balance is related to the distance from the center of rotation, mass, and rotation speed. On a 1 inch shaft running a few thousand RPM the imbalance will not be very significant.
 
Jan 11, 2014
6,566
Sabre 362 113 Fair Haven, NY
balance is related to the distance from the center of rotation, mass, and rotation speed. On a 1 inch shaft running a few thousand RPM the imbalance will not be very significant.
My question, is if the anode is OK to use outside the hull, what makes not OK to use inside the hull?
 
Jan 22, 2008
7,892
Beneteau 323 Annapolis MD
Beneteaus have a small shaft exposure to fit in an outside zinc. There are narrow (7/8?) that are made to fit the small span. This is done to allow water to flow through and out the cutlass bushing. ANY size zinc of 25mm would most likelt fit INSIDE the hull.shaft.
 
Last edited:
Jan 27, 2008
2,967
ODay 35 Beaufort, NC
My question, is if the anode is OK to use outside the hull, what makes not OK to use inside the hull?
Nothing. Should be fine to use inside for a shaft retainer space permitting. I don't see imbalance as a significant problem. If it was a problem the zincs would come pre-balanced but when installing them the screws would have to be tightened exactly evenly and as the zinc wears non-uniformly the balance will change anyway. Worry about something else.