Shaft zincs inside the engine bay?

[Skipper]

I saw a pic once of a shaft zinc attached to the shaft inside the engine bay. Thought it a silly anomaly.
Then I saw another, and another.
Doesn't the zinc need to be touching the water, to, you know, act as an anode?
Have I been stupidly keeping zincs under the boat when I could have been servicing them in the engine bay the whole time?

 

[kloudie1]

Zinc must be in contact with the water to protect the propeller.. They may have been putting an additional one on dry shaft to help with corrosion around a weeping stuffing box?

 

[NYSail]

Or..... 1. A good storage space for your spare; 2. To protect against the shaft spinning out in case it releases from the coupling.

 

[dlochner]

Some have put shaft zincs inside the boat as cheap protection against losing the prop shaft if it separates from the coupling. The shaft can only slide as far as the space between the zinc and the stuffing box. A better choice might be a SS Shaft Collar (https://www.mcmaster.com/#shaft-collars/=18t2na0) but the zinc is cheaper. A 1" 316 SS is over $30, a zinc under $10.

 

[Capt jgw]

Hose clamp works too, only a couple bucks.

 

[Skipper]

To protect against the shaft spinning out in case it releases from the coupling.

Interesting. If that's not the reason, it should be.

 

[Capt jgw]

I once towed in an old Chris Craft motorboat with the shaft pulled out. It hit the rudder and stopped, but there wasn't enough shaft sticking out of the stuffing box to grab and pull it back in. A shaft zinc or hose clamp would have prevented it from happening.

 

[Ted]

A shaft zinc is often placed very close to the bellows of a PSS dripless shaft seal. It would prevent the bellows from extending if the part that is attached to the shaft became loose. Loosing pressure between the polished mating parts would compromise the watertight seal.

 

[JerryA]

That sounds like something I should do.