zinc replacement

[TXS-ALAMO]

I just had the hull cleaned, thru-hulls checked, prop cleaned and zincs replaced. The zincs had been replaced the 1st of April this year with three donut zincs on my 1-1/4 inch diameter shaft. They were almost falling off after only a little over three months. The previous egg type zinc (one) had lasted almost two years but at a different marina for one of those years. The three new large egg zincs were recommended by both the diver and several dock mates. As a matter of fact, one of these said he has a large commercial zinc suspended by a cable and grounded to his engine in addition to his shaft zincs, (he has a note on his ignition key to this effect). I believe that there must be some major electrical currents in the water to cause this zinc problem. I have a Fluke multimeter but don't know how to test the water for stray current. If I can test and find electrical current in the water, what would be my best solutions?

[SoOkay]

what's around you at dock?

For example one season I was next to a tug and went thru 3 sets

[sailingdog]

You have a serious problem at your dock if you went through zincs in just three months. I wrote a post a while back on how to detect a DC-related current leak.

[sailorjim99]

If you have 'live aboards' near you, that can cause the problem.

I haven't found out why but I think it is something to do with the amount of electricity they use all the time as compared to a vacant boat.

Jim.

[Fstbttms]

Originally Posted by sailingdog

You have a serious problem at your dock if you went through zincs in just three months. I wrote a post a while back on how to detect a DC-related current leak.

Rapid anode depletion is far more likely to be caused by an electrical problem aboard the boat in question than it is to be caused by a "hot" dock or marina. While it can't hurt to check for stray current in the water, TXS-ALAMO should consider going through his boat's electrical system as well, IMHO.

[TrueBlue]

I had this problem with my former boat and questioned the possibility of fault by both my marina's AC connections and dockmate's boat. My boat was determined to be the cause of my excessive zinc and running gear corrosion. I had a faulty ground connection to my galvanic isolator - solved by some meter testing and a little rewiring labor by my marina.

Vindication was made to the marina by way of a $550.00 labor bill and I bought my dockmate lunch as an apology for the error through my false accusations.

[TXS-ALAMO]

I am a liveaboard. But this doesn't explain the difference in zinc loss between now and the previous 2 years. There is a home-built aluminium hull ketch that moved in about 6 months ago. The marina, Marina Landing Marina is across from Moody Gardens in a side area of Offuts Bayou in Galveston. The electrical wiring to the docks runs underneath the dock and is "enclosed" in white poly plumbing tubing. It is frequently underwater at very high tides and the Marina cuts electrical power in extreme weather. As an aside. I have had to replace my window ac units three times in the last 2 years as they cease to cool after short times of usage. There are frequent complaints of loss of electrical power and many boats seeking dockage are turned away because the slips have no electical power. Given all this and the fact that my 29d batteries are now dead as doornails, narrowing the cause to the Marina or my boat or both is tricky! Therefore, ascertaining the presence of stray current and the source is the first step.

[Fstbttms]

Originally Posted by TXS-ALAMO

The electrical wiring to the docks runs underneath the dock and is "enclosed" in white poly plumbing tubing. It is frequently underwater...

This is true of virtually every marina I have ever worked in.

[sailingdog]

I am aware of that... and his boat is at his dock... if you read the post I was referring to about detecting DC leaks, it clearly is for tracing leaks caused by a boat's own DC electrical system.

Originally Posted by Fstbttms

Rapid anode depletion is far more likely to be caused by an electrical problem aboard the boat in question than it is to be caused by a "hot" dock or marina. While it can't hurt to check for stray current in the water, TXS-ALAMO should consider going through his boat's electrical system as well, IMHO.

[Fstbttms]

Originally Posted by sailingdog

I am aware of that... and his boat is at his dock... if you read the post I was referring to about detecting DC leaks, it clearly is for tracing leaks caused by a boat's own DC electrical system.

I didn't read your pevious post, nor was I referring to it. I was rebutting TXS-ALAMO's inference that his marina's shorepower system was possibly responsible for his situation because the electrical conduit was submerged at times. This is a very common occurance and not necessarily indicative of a problem with a shorepower system.