Should I replace these zincs?

[Rich Stidger]

Everybody has an opinion, and I want yours. Pictured below are two zincs that I have on my shaft and AutoStream prop. I have always replaced both of them each year, but this year I note that the erosion on both of these is very light. Normally the zincs have much more metal gone.

So, I'm thinking that if the "guideline" for replacement is 40% gone, and these look like maybe 10% gone, maybe I don't need to replace this year. On each of these zincs, you can still read the manufacturer (Canadian Metals) and the part number. One even still has the small paper label attached.

I'm not cheap, well maybe just a little, but does it really make sense to replace a zinc that still appears to have a good deal of metal? BTW, for those of you who have an AutoStream prop and are thinking that the zinc on the prop looks really strange, I machined an adapter for the end of the prop so that I could install a standard $7 3/4" zinc instead of the $40 custom zinc. It works the same but looks strange. $33 stays in my pocket!

If you subscribe to the philosophy to change the zincs yearly no matter what, just qualify your answer accordingly. If you find that your zincs sometimes last more than a year, please let me know your experience.

BTW, I have two new zincs that I can install. I just don't think it is necessary at this point. If I am wrong, please tell me why.

 

[rpell1@msn.com]

Unless you suspect that you're in a "high stray current" area.....they look fine to me! Here in NY, these would easily last until my usual mid-summer prop de-fouling. This is when I usually change them out anyway.

Good Luck and happy sailing....

 

[Maine Sail]

Everybody has an opinion, and I want yours. Pictured below are two zincs that I have on my shaft and AutoStream prop. I have always replaced both of them each year, but this year I note that the erosion on both of these is very light. Normally the zincs have much more metal gone.

So, I'm thinking that if the "guideline" for replacement is 40% gone, and these look like maybe 10% gone, maybe I don't need to replace this year. On each of these zincs, you can still read the manufacturer (Canadian Metals) and the part number. One even still has the small paper label attached.

I'm not cheap, well maybe just a little, but does it really make sense to replace a zinc that still appears to have a good deal of metal? BTW, for those of you who have an AutoStream prop and are thinking that the zinc on the prop looks really strange, I machined an adapter for the end of the prop so that I could install a standard $7 3/4" zinc instead of the $40 custom zinc. It works the same but looks strange. $33 stays in my pocket!

If you subscribe to the philosophy to change the zincs yearly no matter what, just qualify your answer accordingly. If you find that your zincs sometimes last more than a year, please let me know your experience.

BTW, I have two new zincs that I can install. I just don't think it is necessary at this point. If I am wrong, please tell me why.

For what zincs cost vs. shafts, props etc. I'd change them. I think I just paid about $6.00 for two Camp zincs at Hamilton Marine. As usual I could not get my preferred Godfrey zincs in time. Better planning next year, hopefully...:neutral: Keep in mind that they may not be worn because you may not have had good electrical contact.

The lack of erosion also looks indicative of an "isolated" shaft? With an isolated shaft, which goes against ABYC standards, and a SS prop and Aquamet shaft the zinc wear would be pretty minimal anyway as your electrical galvanic separation would be very low mV wise between the prop and shaft.

I clean the shaft side of all zincs before installation with wet sand paper. This removes any surface oxidation and preps them for good electrical contact to the shaft. I find this prep work causes them to wear more evenly. I also clean the shaft with wet sand paper to also get good electrical contact. Most people clean the shaft but never think to clean a new zinc. I then install them and give them a light tap with a brass or phenolic hammer to "set" them.

The zincs will also get a layer of oxide between the shaft & zinc after a haul re-launch making the electrical contact even more suspect. For the cost it would be a no brainer for me....

 

[Bob S]

Maine,
What's the reason for wet sandpaper. I use do the same process as you but with dry paper and blow the dust our with an air gun?

Would there be a problem just adding a new zinc and leaving the older ones on? They do look pretty good.
Curious minds want to know

 

[Jake N Eggs]

Just out of curiosity, is the zinc in the OP picture too close to the strut? Could it possibly restrict water flow through the bearing? And now that my 56k is churning is there a standard for the distance between the zinc and the strut?

Sorry Rich, don't mean to hijack.

 

[seadaddler]

Repell 46

Hi and don't mean to hijack but what's it like in Shepshead Bay Brookly these days.
My wife was born in Canarsie and I in Red Hook and my parents always loved taking me and my 3 sisters to Sheepshead bay and walk along by the boats than go eat all kinds seafood.
We moved to LI in 1959 and must be a 40 years since we been to Sheepshead bay.
Nick

 

[Blitz]

Did you change anything electrically last year that could have minimized the erosion of the zinc?

I ask this because I installed a galvonic isolator last winter and have found that my shaft zinc showed little erosion as well. I'm going to leave the old one on and install an additional new one for security. I normally only install one shaft zinc but they used to be gone or close to gone by the end of the season before the isolater install.

Looking at yours, of you have good contact, I think I'd change the prop one, leave the other. I'd also check on it during the season. But then again, they are cheap insurance.

 

[Don S/V ILLusion]

Hi Rich
My 2 cents is that this is a "peace of mind" issue. I wouldn't bother replacing them if I was confident they were good but I would do one thing for my mental health - remove them, clean the contact surfaces of both the zincs and shaft/ prop and reinstall just to confirm minimal resistance between the materials. Without doing that as a min, it would keep me awake at night.
Have a great season

 

[Benny17441]

I subscribe to the theory of not throwing away anything that is still good and useful. The thing about replacing them yearly may work for those that do not want to have to check them periodically. We have a diver that cleans the bottom about once a month (believe me it seems like in just two weeks the stuff is back) and he inspects the zinc collar which he will replace when it is about 80% gone. Never have we encountered the issue when the zinc may have desintegrated in a month's time. With boats coming an going we have had periods where they have to be replaced in six month and then at a year and a half at other times.

 

[srhummer]

I really think you should change both and send them to me for further analysis. I can let you know how long it would have taken to get to 40%. I can send you the results right after I take them off my boat.

 

[Witzend]

Some zincs have a copper bee bee in them to help maintain good electrical contact with the shaft. Anyone know if this idea really works?

 

[Rich Stidger]

Thanks, all. I could have predicted that the "peace of mind" issue would be raised, as well as the "if it's not broke, don't fix it".

Answers to your questions-

I clean the shaft areas each year with a plumbers sandpaper tape (dry) and they are clean. I have never cleaned the inside of the zincs but they are always bright and shiney. The zincs that I have used for the last several years (NOT JUST LAST YEAR) are the type without a copper ball inside. The manufacturer's claim is that they are precision machined for a tight fit and that the copper ball is not required nor is it necessary to hit the zinc with a hammer to create a "better" contact. I have never noticed any difference between the copper ball type and the ball-less type in terms of erosion over a six month season.

Nothing has changed this past year of which I am aware. My boat lives on a mooring well out in the harbor away from shore power sources- but this is nothing new either. The shaft and the prop are both a flavor of stainless steel, so I don't expect a lot of erosion on the zincs, but this past year the erosion has been less than "normal".

In past years I have had more erosion than during the last year. I cannot explain why this happened.

If I measure the electrical resistance between the zinc and the shaft and find that it is as close to zero as just the meter leads, does anyone think that is sufficient to indicate good connection to the shaft? If I remove the zinc I wonder if I could re-install it with a quality connection?

I have not observed any derogation of the shaft or prop due to a poor zinc connection, so I tend to believe that the zincs are connected well right now.

I don't have my prop and shaft cleaned or inspected during the year, but I could inspect it myself after a couple months.

srhummer- Thank you so much for your most generous offer. I think I'll pass for the moment.....

 

[TENACITY CS36T]

Put an ohmmeter on it, one lead to the shafts and one lead to the zinc and ring it out to check continuity.

 

[bffatcat]

throwing away good zincs

Id listen to srstrummer send them to him so he can get the rest of the good use out of them
Zincs are supposed to be sacrificial from the picture your Zincs havent been sacrificed

 

[Chris Burti]

I confess that I change every time I haul, which is normally once a year and I have a galvanic isolator installed, so they usually look pretty good.

Some questions are best answered by another question.

What will it cost you if you don't change them and they don't last?

These can be much further along the electrolosis trail than they appear and I have personally seen them removed where they look very good on the shaft, but are virtually hollow on the inside...if you are going to use them, take them off and inspect them thoroughly.

 

[rpell1@msn.com]

The more things change...........the more they stay the same. Fewer fishing boats, but more Dinner Cruise boats. Fewer "old-time" restaurants, but more total restaurants. The same Boat and Yacht Clubs though.....Varuna Boat Club, (in the Bay since 1910), Sheepshead Bay Yacht Club, Miramar Yacht Club, Stella Maris store and marina.....but no more BayEnd Marina. The demagraphics have changed significantly and the Bay is still crowded as soon as the weather warms. You should come to visit. You certainly won't be dissappointed.

Happy Sailing.

Hi and don't mean to hijack but what's it like in Shepshead Bay Brookly these days.
My wife was born in Canarsie and I in Red Hook and my parents always loved taking me and my 3 sisters to Sheepshead bay and walk along by the boats than go eat all kinds seafood.
We moved to LI in 1959 and must be a 40 years since we been to Sheepshead bay.
Nick

 

[All U Get]

Hi Rich,
If you want a different thought from half a mind, change one. My Catalina had one shaft zinc and the year I bought a new prop, the zinc had fallen off. After that I used two, changing one a year. (I did say half a mind)
All U Get
PS Was that a 1" shaft?

 

[Cool Beans]

I have asked people in and around my marina and they say a zinc should last at least a year around here. I put new Zincs (1 shaft, one small one on the strut) last April. Out of curiosity, I'm going to leave them on there until they need to be changed. last diver said they looked fine and didn't need to be changed. It's been 13 months so far

 

[Rich Stidger]

PS Was that a 1" shaft?

It is a 1.25" shaft.

I have no galvanic isolator and the shaft is connected to ship's ground through the transmission coupler only. I have never had really badly eroded zincs, but these are light by any measure.

I am thinking that I will verify the lowest possible conductivity between the shaft zinc and the shaft itself and I will replace the one zinc on the prop. I'll try to take a look part-way through the season and see what I have at that point.

I wonder how often we all just replace stuff because it is "customary" or for "peace of mind"? Here is another case in point....

I have Racor primary filters on my two diesels - auxiliary and generator. I have always replaced them every other year with about 250-300 running hours on them. Flow rate is 0.75 for the aux and 0.45 for the genset.

Do they really need replacing for the number of gallons run through them? Who knows? I've never had a plugged filter that affected the engine running.

This year I am installing vacuum gauges on each filter and I plan to change the filter based upon the vacuum reading as a measure of trapped crud. Will this mean that I replace the filters every 2 years or 4 years? I guess I will find out. I don't know of any spec that says that the filters have a lifetime regardless of the amount of crud that is filtered out, but I will look for one.

Anyway this is just another example of maintenance by time vs use.

 

[Don12364]

My Practice

If the old shaft zinc looks to still have some life left in it I just put a new one alongside it - though I never have more than two. Normally by the following season's lift out the original one has disappeared.
In your case the erosion is so slight that I question whether it is actually bonded to the shaft so I would remove it and clean up both shaft and inside of the zinc with wet & dry and put it back on - together with the new one you just bought anyway.