Zinc Question

[Rich (P303)]

Fellow zinc-o-phobes...

Quick question for you... being the second season with a boat and zincs.

The first year a yard put a prop zinc on... when it was pulled in the fall... zinc was completely gone... I mean like it was never even there.

This season I put one on myself... compressed it with opposing taps of a hammer... tightened it up some more... same results this fall... no zinc.

I have a 13 HP Yanmar with a 1" shaft... the boat is in the water for about 5 months on a mooring.

Is this normal to deteriorate and spin off? What am I missing? Any suggestions besides going diving halfway through the season?

I have a line cutter "Spur"... that was still there and about 1/4 left.

Glad to be back,
Rich
:cussing:

 

[RichH]

One question to ask ... is there any evidence of electrolysis of 'other' underwater metal parts?
If no, then you had 'just enough in zinc anode surface area'.
If yes, then the answer is obvious ... not enough anode surface area.
If you dont know ... then get a reference cell to measure the electrolysis potential of your boat http://www.boatzincs.com/corrosion-reference-electrode.html

You can have 'too much' or 'too little' anode ... and only a reference cell will answer the correct question. You could also have an electrical leak in a bilge pump or bilge pump switch, etc. Why guess?

 

[CalebD]

I have to agree with RichH. I put a zinc on our prop shaft once maybe every 1 or 2 years in the Hudson River on a mooring. There is always some of the collar zinc left over on the shaft.
You must have some kind of short or electric fault happening that is helping to corrode your anode (zinc). If not that then you are keeping your boat in a marina at a slip where a boat neighbor or the dock itself has an electrical fault that is prematurely degrading your zinc.

 

[Mike8193]

zinc

I am surprised on a mooring your zinc would "dissolve" in one season. I am on a mooring for 5 months a season (fresh water) and I haven't had to replace the original zinc yet (four seasons). Something is degrading your zinc prematurely ( I have a prop shaft zinc on a 3ym20 yanmar). Mike

 

[bobtigar]

I believe the zinc is coming off. If this is a donut type make sure you are using the correct size. When you tighten the zinc up , tap it with a hammer on both halves and then tighen a few more turns . Bob

 

[alexco38]

If your Spur is 1/4 left and the zinc is gone you have serious grounding problem. First of all, dieconnect any DC ground from the bonding ground (keel etc.)

Use a volt meter and measure the shorepower ground to the motor. The zinc doesn't eat itself. It is the current flowing between your shorepower ground to the drive shaft. Have you heard of a galvanic isolator? You can make one youeself with 4 diodes.

 

[Bill Roosa]

You have a leaky wire in the water somewhere.

Arm yourself with a multi-meter and start investigating.
While still in the water at the mooring:
Turn off everything, Main and secondary CBs and pull the fuse on the bilge pump and radio (and anything else that is) "always hot" circuit
Take off the battery + and connect the multi-meter set to read milliamps between the + terminal and the + terminal wire.
There should be NO current. If there is then you have a leaky wire in the primary power circuit to the panel or "Always hot buss"
Put the fuse back in the bilge pump circuit and retest. You should get NO current unless the pump cycles. If you do get current flow then the bilge pump circuit is leaking.
continue checking circuits in this fashion till you find the one that is leaking.

The Great Roosack predicts you will find a wire in the bilge pump circuit that has a very small chafe spot or insulation gone bad from years in the water or wire splice that is underwater and leaking.

 

[Rich (P303)]

Re: You have a leaky wire in the water somewhere.

Ahh.. such a simple question. I new it wouldn't end here. Electricity isn't my specialty.

I should clarify... the spur wasn't 1/4 left... just the spur zinc. Prop and prop shaft look fine. I have a shaft saver that separates the shaft from transmission... to what degree I do not know.

I have no shore power... and am at least 1/10 mile out into the mooring field.

Bilge pump brand new and no wires in any water.

Guess I'll proceed with the reference cell thing... along with a multi-meter. I can do this on the hard... and not in the water... correct?

Bare with me here... I have a small grounding plate on the keel with about a half a dozen green wires going to it from the rudder packing gland; mast step; stanchions etc... Should the engine block be one of those wires?

Thanks for your help,
Rich

 

[sailingdog]

If you're on a mooring, chances are very, very high that your boat has a DC leak someplace. I wrote this post up for another sailing forum, and think it will help you.


If you want to test to see if you have a DC-based ground leak, the test for that is rather simple. The steps for seeing if you have a DC-ground leak are as follows:

First—the preliminary diagnosis test:

1) Turn off all equipment and disconnect any solar panels
2) Disconnect the positive side of the battery banks.
3) Leave the main battery isolation switch turned on for the bank in question
4) Set the meter to VDC mode, range appropriate for your battery bank
5) Connect the meter between the positive terminal and the disconnected cable

The meter should give no reading. If it reads XX volts for your XX VDC system, one of two things is happening.

1) You've left some equipment connected and turned on. This could be a bilge pump, a power feed to a stereo for the radio's memory and clock functions, or a hard-wired fume detector.

2) If you've disconnected all the "hard-wired" equipment and still get a reading, then you've most likely got a ground leak in your boat's DC system.

The Ground Leak Check:

1) Set the meter in Ohm mode and set it to the lowest range (x1).
2) Connect the leads of the Ohm-meter (or multimeter in Ohm mode) to the disconnected positive lead and the negative terminal of the battery.

The meter is now reading the resistance of any circuit to ground that exists in the boat's wiring. The reading on the Ohm meter display can help you identify the cause of the leak.

0-10 Ohms means it is most likely a piece of equipment left on
10-1k Ohms is a low-drain piece of equipment left on, or a serious ground leak
1k-10k Ohms is a minor leak
10k+ Ohms is an insignificant leak

How Big is The Leak?

The ammeter function of the multi-meter can tell you what the current leakage is. If your meter can read up to 10 Amps DC, then you can use it to measure amperage for leaks down to about 1.3 Ohms resistance on a 12 VDC system, or 2.6 Ohms for a 24 VDC system.

To see how big the leak is, put the probes on the positive battery post and the disconnected cable. The meter readings can be interpreted as shown:

<1mA — insignificant leakage
1–10mA — minor leakage
10mA–1A — major leak or some equipment left on
>1A — Usually some equipment left on.

Since your on a mooring, I seriously doubt it is an AC side leak, unless your boat has an inverter with a problem.