Zincs?

[Mike Oatsvall]

We seem to go through a lot of zincs at our marina. I thought I would augment the two 1" zincs on the shaft with one of these hang over the side guppies. I've seen them on other boats attached to various places like the arch, railings, etc.
Electrically speaking where is the best place to connect it to do the most good? Is the arch on a H33 actually grounded? Should I run a wire directly to the engine block or where?
Thanks for any input.
Mike Oatsvall
Four Winds, 2004 H33
Oriental, NC

 

[JoeWhite]

Mike - you did not mention how often you are having to replace the zinc and where are these zincs - prop shaft? I would ask the neighbors if they are having to replace them often as well. I replace mine once a year - the ones on the prop shaft and the strut. If it is much more than that - then check the ground and wiring on the off shore power plug and inside your boat. An other boats bad wiring can also cause you to use up more zincs as well. Using the engine block as ground is best.

 

[Mike Oatsvall]

I go through about 1.5 zincs in a quarter. They are on the prop shaft and my immediate neighbors experience the same rate or similar rate of usage. I do not keep the AC connected when we are gone.

 

[JoeWhite]

I am not sure what you mean by 1.5 zinc. Do you replace all three shaft and strut zinc every 6 months?

 

[Mike Oatsvall]

Every quarter at least one 1" zinc is completely gone and about 50% of the second zinc is remaining. I have two shaft zincs on the boat. No struts.

 

[Don S/V ILLusion]

First, you can create the same effect by using a merc cruiser or any other sizable zinc rather than the very expensive guppie.
Second and equally important, make sure there is no resistance between whatever you use and ground. Even a very slight resistance will make it useless so the connections to the ground point is critical. Usually, deck mounted hardware isn't electrically well-connected so it is often better to run the underwater zinc you use DIRECTLY to the engine ground or even better, the shaft itself (using a hose clamp).
If you go that route, make sure you disconnect it before getting underway or - surprise!

 

[DianaOfBurlington]

Zincness.

The zincs should be as close to the underwater metal that's going to be eaten if the zincs are not there. That means on the strut, the rudder shaft or, on older motorboats, the metal rudder blades.

There is no drawback to having too big of a zinc nor to having too many. The difference is not made in the size of the metal thing but in the chemical makeup of the metals. Note that they all begin to corrode around their own zinc-plated steel screws-- an example of what would happen to your bronze shaft without them.

An oversized shaft zinc, or two or three shaft zincs, will do no damage and may cost you a whole whopping $20 more per year.

In the meantime you might want to investigate why you are losing zincs so fast. In nice waters the typical collar-type shaft zinc should last easily two seasons or more (though prudence says to replace it annually anyway). Many variables could be at play here, not the least damaging of which could be loose 115VAC current in the water. Someone along the same dock could have a ground fault and be sending hot current to his grounding plate or keel. I have also heard of businesses nearby who either deposit weird metals into adjacent waters or allow stray electrical current to go to ground there. In any event this is not a benign situation. There may be local code violations or EPA problems at hand.

 

[jtm]

Marc- not all zincs are created equal- some are more prone to be eaten than others. I go thru about half of each Martyr "egg" shaft zinc a year/sailing season. Sounds as if there could be a fair charge in the water- our marina owner will take charge readings in the marina if one feels that "something is goin on". You may need to concern yourself that the charge could be serious as some people may need a galvanic isolator etc and it could be dangerous to get in the water in some area. So the marina has some interest to ensure things are safe. I'd ask the marina to test around to be safe!