Zincs

I'm getting only about 5 mounths out of a set of zincs (1988 40' DC). I think I should be getting better than this. We relocated the boat to a temporary location in S.C. recently, and the problem persisted, so apparantly this is not a marina problem. A couple of years ago when I became concerned I had it tested by a surveyor with a background in electrolisis. He said the problem is not the boat. But it's begining to look like the problem may well be the onboard as we have been a transient lately.

Am I wrong to think that I should be getting more than 5 months out of a seto of zincs?

If not, anybody got an ideas what might be the primay culprit?

I have also heard that Hatteras is installing something on all new vessels to minimize this problem (but it's not a galvanic isolator)?

Thanks,
Capt'n Bill

Check for DC leakage and bonding system integrity.

Start by turning off EVERYTHING. Disconnect any "soft button" electronics (those without hard-wired power switches, e.g. chartplotters, etc)

Turn off all breakers and disconnect the batteries.

Connect a VOM across the battery leads, set to ohms. It should read infinite.

Turn on your DC breakers one at a time. When you find one that makes the meter read something, chase it down and find out why. If you find a soft-power-switch item, disconnect it and keep going. If not, you have something leaking current somewhere. Common items that do this include bilge pump switches.

If you get to "all circuits on" and still have an infiniite reading, then the problem is not on the DC side per-se.

Now verify all bonding connections. With the meter set to "Ohms" check from EACH bonded item (all seacocks, etc) back to the bonding strips along the hull. All must read less than 1 ohm (lower is better; a good connection is under 0.1 ohm.) Check the bonding system to DC negative (it'd be nice if they were separate, but its almost impossible to do since the engines are connected to DC negative.) If you find any bad bonding connections fix them.

Now do the same on the AC side, but BE CAREFUL TO MAKE DARN SURE ALL AC FEEDS ARE OFF FIRST! Note that it is HIGHLY unlikely that the AC side is responsible for this.

If you go through all of this and find nothing suspicious, and you're not plugged into shore power (or either have an isolation transformer OR have eliminated that as a cause), then its just your boat and its characteristic galvanic difference between the metals connected to the bonding system, and there's not much you can do about it other than to increase the size (not the surface area though) of the zincs so they last longer.