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Shaft Zinc(s)

Brian K

Member III
My 1988 Ericson 32-200 has 2 zincs on the 1" prop shaft. Having moved the boat from salt water to fresh, I'm replacing the zincs with magnesium anodes. The question is, do I need 2 anodes or will one be enough?
 

Shadowfax

Member III
Better Safe Then Sorry

Depends on the stray current in your new location. I'd go with the two and see what it looks like next year when you pull the boat. An extra anode is cheaper then the damage done if one wasn't enough.
 

Mort Fligelman

Member III
Shaft Zincs

I had a Seidelmann 299 with a Yanmar 2QM15 with a Bronze shaft from 1979 to 2006 in Lake Michigan.....Major marinas.....never even thought about zincs...never had one.....never a problem...shaft looked like new after 26 seasons (May to October).

Knowing what I know now after being in salt water and having been warned about stray current........the Zincs can't hurt......better safe than sorry....

My $.02 Worth

Mort Fligelman
1987 E35-3
Acapella
Boca Raton, FL
 

rwthomas1

Sustaining Partner
I don't remember the specifics but you can have trouble from too many zincs as well. Caution would dictate installing one and checking on it halfway through the season. Install another if needed. RT
 

Chris Miller

Sustaining Member
I don't remember the specifics but you can have trouble from too many zincs as well. Caution would dictate installing one and checking on it halfway through the season. Install another if needed. RT

I've read horror stories about this as well.
Our local Benny Dealer's mechanic suggests hooking one of those fish annodes to your ground plate or the ground on your engine as a better alternative to having more than one zinc on the shaft.
Chris
 

Tom Metzger

Sustaining Partner
Brian - I have almost thirty years of inboard experience in fresh water and keep a single zinc on my prop shaft. It lasts in excess of ten years. I have always been in a large marina.
 

Brian K

Member III
Shaft Zinc

Tom, do you use a zinc anode or a magnesium anode. My surveyor was careful to point out that in fresh water you should be using magnesium, not zinc. 10 years is a very long time! I'll probably try 1 magnesium anode and check it when I dive in on a hot summer day.
 

Chris Miller

Sustaining Member
Brian - I have almost thirty years of inboard experience in fresh water and keep a single zinc on my prop shaft. It lasts in excess of ten years. I have always been in a large marina.

There really are days that having a freshwater boat would be cool...
 

Blue Chip

Member III
Alternating Zincs

Apparently a common practice here is SF Bay is to have two shaft zincs.
The diver that scrubs the bottom comes around on a contract every three months. At that time the diver switches out ONE of the zincs. Thus you always have (sorta) one that is approaching 6th months old, and the other is nearing three months old. The older one of course gets switched out. Been doing this for over 15 years on our 32-200 and it works really great.
Frankly, I think it all depends on the quality of your docking situation...marina (good or bad) mooring balls, no shore power...fresh or salt, etc.
 

Emerald

Moderator
Whether one or two zincs on the shaft, place at least one several inches in front of the strut instead of behind the strut. This is just a last chance preventive measure to keep your shaft from spitting out the back of the boat if you have a failure at the hub side of the shaft. It is important to leave several (let's say 2 min.) inches between the zinc and the strut to make sure you don't interfere with water flow through the cutless bearing.

If you have too much zinc, I believe you will know by odd things like the bottom paint "burning off" around the zincs. A friend had this happen with a flat sand dollar type zinc on a bronze strut.
 

Sean Engle

Your Friendly Administrator
Administrator
Founder
suggests hooking one of those fish annodes to your ground plate or the ground on your engine..

I had both on my boat (my marina was so hot you could cook in the water). I ran a ground wire back to one of my cleats and then could use is as a clamping source for the fish.

//sse
 

Tom Metzger

Sustaining Partner
Magnesium shaft anodes?

Since the subject came up I have looked into it a little on the net and find that most references to magnesium anodes come from the UK. I didn't find any suppliers of magnesium shaft anodes in the US.

Torresen doesn't carry them and they are located on the Great Lakes.

What gives?
 

Brian K

Member III
Magnesium Anodes

Tom, I bought 2, 1" shaft magnesium anodes from boatzincs.com. The mag anodes are about $18 each while zincs are about $8. I called them and they had never heard of a mag pencil anode for the engine, so I went with the standard zinc pencil anode there. My surveyor said if you put a mag anode in salt water its almost like putting Alka-Seltzer in water; they disolve very quickly. On the other hand, zinc in fresh water is apparently not very effective as an anode. That's why some in this thread noted the longevity of zinc in fresh water.
 
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