Shaft Zincs on Year-Round Cruisers

[Bash]

Okay. So let's say that you plan to haul the boat out every two years for fresh bottom paint. And let's say that you go through a zinc ever six months. So, rather than put on a single shaft zinc and carry three spares aboard, wouldn't it be better just to install four zincs on the shaft and assume that you've got it covered until the next haul-out?

Let's assume that you're planning to dive the hull periodically and make certain that the zincs are holding up.

What am I missing here?

[Stillraining]

I run two at a time FWIW.... and they both get ate up the same amount and are needing changed in as few as 3 months.

Not enough water time with my boat yet to know if I have stray current issues.

[noelex 77]

Too much zinc can cause problems, but how much is too much?
Putting more zincs is certainly better than having none, but 4 may be a bit too much if they are large particularly for a non metal boat.
I have 3 on the propshaft of my aluminium boat and usually only need change one at hallout.

[Hudson Force]

I have space to fit one 2 1/2" shaft zinc that is fitted with the use of an allen wrench. It's not difficult for me to free dive to clean the shaft space;...up for a breath......place the zinc with a loose first threading;.... up for a breath.....and return to tighten the allen bolts. Take care and joy, Aythya crew

[Vasco]

Changing zincs is one of the easier boat jobs. Just hold your breath. Mine usually lasts four to five months.

[anjinsan]

Mind if I throw in a question here? Helping a friend, looking for the zinc in his heat exchanger pm a Yanmar 3 cylinder diesel. Anyone know where its hidden? On my universal, its a pencil zinc with a threaded bronze cap attached. It screws right into the side of the heat exchanger. Cant find anything on his Yanmar...Thanks for your help in Advance.

[GordMay]

Originally Posted by anjinsan

... looking for the zinc in his heat exchanger pm a Yanmar 3 cylinder diesel. Anyone know where its hidden? ...

Don't think Yanmar uses zincs.

[capt_douglas]

I follow CaptForce on the shaft zinc replacement. The process can be a bit intimidating the first time but after that it's fairly straightforward.

The only ones I don't replace underwater are the zinc on the end of the propeller and the Dynaplate.

[anjinsan]

that would explain it. But he does get a lot of debris build up in his salt water exhaust.

Thanks Gord.

[S/V_Surya]

Zinc usage I do not think is extended by putting more zinc’s on. It may help extend the life but as we all know dissimilar metals in contact with each other cause the current. Adding more metal won't help. I read an article on this some place a long time ago. Will check around and see what I can find.

[fstbttms]

Originally Posted by S/V_Surya

Zinc usage I do not think is extended by putting more zinc’s on.

In fact, it is. Generally speaking, if one zinc lasts X months, then two zincs will last 2X months. However, there is a point of diminishing returns and it is absolutely possible to overzinc. Impossible to say from an office chair if Bash would reach this point with 4 shaft zincs, but it is possible to say that 4 shaft zincs is quite unusual.

[hummingway]

In addition to two zincs on the shaft I've run a wire a from my engine to the cockpit combing and attached an old zinc to it that goes over the side when not moving. There's a few folks doing this at my current marina. The thinking is that it slows down the loss of the more expensive zinc on the prop shaft.

[Sailmonkey]

I've got a hell of a time fitting one zinc much less four!!