Zinc gone in 1 season

[wchevron]

i put a new zinc on the shaft at the beginning of the season. just checked it last week on haulout to see how it made out over the summer. it's gone. would it corrode in 1 season or did it fall off most likely? i had brought the old one when i purchased the new one so i know it was the right size.

[Giulietta]

Really depends on how you sail, how much ou sail, if your boat has stray currents, if the marina has stray currents, if the boats near yours have stray currents, if you have a galvanic protector...etc.etc..

But generally they are desigend to be replaced on a year basis. I replace mine every 6 months..just in case, besides worn out zincs are rough and cause drag

[sailingdog]

If the zinc is completely gone in one season, I'd say you have an electrical leak, either at the slip, a nearby boat or on your boat, or the zinc is undersized for the task at hand. You won't know this without getting out your VOM and checking things.

Another possibility is you got cheap zincs with the wrong alloy in them.

Most zincs should last at least a season.

[JHJensen]

wchevron
Having an anode go in one season may not be problem. Need more information. Anodes should be replaced when they are 50% consumed. Are you sure you have a zinc anode?
1.What kind of boat and the location ( are you salt or brackish water)?Did you check the anode during the season? How long is your season?(What do you define as the length of the season?)
2. I s the vessel new to you and is it in the same spot it was last year?
3. Are you on a dock or a mooring? If on a dock are you hooked to shorepower? If so do you have a galvancic isolator installed on the vessel.
4. What type of propeller and shaft do you have? Materials and number of blades on the prop?
5. Does your boat have a bonding system and if so what kind of shape is it in?
6. What type of keel ? material? Internal or encapsolated? If external what kind of shape is it in? is bare metal showing?

Some pictures of the running gear and keel would be good as well.

Hope that gets you started. You can PM me if you want. Are you going to wet store or up on the hard?

John
ABYC Corrosion Tech.

[Fstbttms]

Originally Posted by wchevron

would it corrode in 1 season or did it fall off most likely?

It's impossible for us to determine whether the zinc depleted entirely in that time or if it fell off prematurely because it wasn't installed properly. It is unlikely that you bought an inferior zinc. Most available in the U.S. are made to Mil-Spec standards and are of high quality. Further, there are many electrical variables that can affect zinc longevity; from issues aboard your own boat or a neighboring one to problems with the shorepower system.

I find that zincs should last at least 6-9 months. Dramatically more or less and it's time to look for a reason. My advice is to install two shaft zincs next season. Your Catalina 30 has plenty of room on its 1" shaft to fit them and you will not be overzincing the boat if you do. At the very least it's cheap insurance. If you find both of them are well-depleted or missing at the end of next season, call a marine electrician in to run down the problem.

[djodenda]

Just a datapoint, but I use 2 oval zincs on the propeller shaft of my C30, which is moored in a marina in salt water.

They are about 25% used up in six months....

[ebs001]

As your data indicates you are from Rhode Island I think is safe to assume your boat is in salt water and at a marina. If it is attached to shore power I think it's fairly normal to have stray currents significant enough to cause considerable erosion of your zincs. In North America the earth is used as the return on the neutral side and so we have all kinds of stray currents. Having said that, the fact that yours is completly gone I suspect it's fallen off. The mounting scew holes in most zincs tend to be the weakest point and even a little erosion will cause the scews to either become loose or work right through the retaining holes.

[wchevron]

Originally Posted by JHJensen

wchevron
Having an anode go in one season may not be problem. Need more information. Anodes should be replaced when they are 50% consumed. Are you sure you have a zinc anode?
1.What kind of boat and the location ( are you salt or brackish water)?Did you check the anode during the season? How long is your season?(What do you define as the length of the season?)
2. I s the vessel new to you and is it in the same spot it was last year?
3. Are you on a dock or a mooring? If on a dock are you hooked to shorepower? If so do you have a galvancic isolator installed on the vessel.
4. What type of propeller and shaft do you have? Materials and number of blades on the prop?
5. Does your boat have a bonding system and if so what kind of shape is it in?
6. What type of keel ? material? Internal or encapsolated? If external what kind of shape is it in? is bare metal showing?

Some pictures of the running gear and keel would be good as well.

Hope that gets you started. You can PM me if you want. Are you going to wet store or up on the hard?

John
ABYC Corrosion Tech.

john
1. 1978 catalina 30. narraganset bay, ri. salt water. season (in water) 6 months. i didn't check the anode during the summer. mostly day sails every weekend with a few overnights.
2. i bought it last fall. was previously located in connecticut.
3. it's at a slip with shore power. not sure about the galvanic isolator
4. brass shaft & 2 blade brass prop.
5. by bonded do you mean grounded? i know the engine is grounded to the hull. there are 2 screws that go through the hull that have wires attached to them. i painted over them when i repainted the bottom last spring. i haven't traced the wiring to them but i assumed they were for grounding. they appear to be in good condition as well as the internal wiring.
6. the keel is a lead fin keel where it is attached to the hull it is fiberglassed to the hull. the bottom 3/4 is bare lead. this past spring i put 4 coats of barrier coat & 2 coats of anitfoul on it so it's pretty well covered. the only part i couldn't paint were 2 small 4"x4" sections on the bottom of the fin where it was resting on blocks while on the hard.

[sailingdog]

wchevron-

The prop and shaft are BRONZE... not brass.

[wchevron]

sorry, i always get the two mixed up.