Perry nut zinc alternative?

[Bob_S]

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Hello All.
I have a question about finding an alternative to using the Perry nut zinc on the end of my CD27 shaft. First of all, I have to grind out the flats on the interior of the zinc with my Dremel to fit over my prop nut. I have tried several different nuts. Also in our marina the zinc never makes it through the whole season so my anti corrosion protection such as it is, will dissolve with the zinc. I was wondering if anyone has successfully used one of those Hang tuff zincs (or similar hang over the side zinc) properly bonded to the engine block. I'll have to devise a convenient way to hook it up but it seems like it should work.( I think lol) There's not enough room and I'm not sure it's advisable to use one of those shaft zinc collars without milling it down some. Anybody else have to find an alternative to the Perry nut and want to offer some ideas? Thanks to all..!!!
Best,
Bob S

[Walter Hobbs]

I looked at the end of shaft type zinc for my 27 this season. But after measuring a 28, also in the yard, looks like clearance with the rudder on a 27 may be minimal if at all.

Last year I sliced a section off a "doughnut " style zinc to narrow it down to fit between the prop and shaft log. It worked for the season, probably will do it again. Not very elegant. Your results may very.

I don't see why a "hang overboard " type zinc wouldn't work. I don't think it could hurt.

[mgphl52]

If nothing else, maybe the "hang over" zinc will extend the life of the Perry nut zinc?

[wikakaru]

I was wondering if anyone has successfully used one of those Hang tuff zincs (or similar hang over the side zinc) properly bonded to the engine block. I'll have to devise a convenient way to hook it up but it seems like it should work.

I owned a metal boat for 17 years, so I have a lot of experience with zincs and galvanic issues. Stray electrical current can sink a metal boat in a matter of days, so it is serious business for metal boat owners, but the same principles apply to protecting underwater metal on fiberglass boats.

Hang-over-the-side zincs (the proper term is "fish", and one commercial vendor even molds theirs in the likeness of a fish to emphasize the connection with that name) are a good addition to other underwater zincs while you are in a marina, but they are not a replacement for a proper shaft zinc or other underwater anodes.

The commercially available zinc fish I have seen are rubbish. Avoiding voltage drops in the system is critical for proper protection, and the commercial zincs I have seen have stainless steel wire, which has a huge voltage drop compared to copper, and use cheap chrome-plated steel battery spring clips that quickly rust and lose any electrical connectivity. You have to make the electrical path to your fish at least as good as the electrical path to your shaft zinc to get any protection from it.

If you are going to use a fish, I suggest that you build your own. I used a weld-on zinc anode and drilled two holes in one of the weld tabs. One hole is for a piece of small rope to support the weight of the fish, and the other is drilled and tapped for the electrical connection. Use only high quality heat-shrink marine electrical terminals. Use only tinned copper marine wire. Use only copper (not stainless) screws for the electrical connections. Make the rope short enough so that the electrical connection on the fish is suspended above the water but the zinc is in the water. The connection on the boat end will depend on what you have on your boat, so I will leave that up to you to figure out, but I can't emphasize enough that keeping the electrical losses low is critical.

You should also consider whether your shore power and/or electrical system onboard is causing your zinc to erode prematurely. I would be surprised if the galvanic action between your bronze prop and your stainless prop shaft would cause enough galvanic activity to eat away a properly sized zinc in one season, so you should really try to find out what the problem is that is causing the zincs to deteriorate so quickly.

You can hire a marine surveyor who should have the specialized meter for testing galvanic activity. (Ask first. Preferably, find one who specializes in metal boats even though your boat is fiberglass, because they will have the expertise to diagnose the issue.) The procedure is to hang a special anode into the water, connect the other lead of the meter to a good ground, and test every electrical device onboard to see if one of them is causing the unwanted electrical current in your system.

If you have a shore power system, you should consider installing a galvanic isolating diode, and possibly an isolation transformer. The surveyor should be able to tell you if you need one or both.

You may also want to consider a "shaft saver" or "drive saver" that is designed to electrically isolate the shaft from the transmission. It will require shortening the prop shaft, so it's something you will have to do when hauled.

I realize that some of these are fairly big fixes to an apparently small problem, but if your prop or prop shaft fails right when you need it most just because of some galvanic activity, then that small problem can turn into a big one in a hurry.

Smooth sailing,

Jim

[wikakaru]

P.S. If you add a drive-saver without shortening the shaft, or only partially shorten the shaft, it may provide enough clearance for a donut collar zinc instead of the nut zinc. They make donut zincs in varying widths, so you should be able to find something that fits on the shaft but doesn't block the flow of water to the stuffing box.

Smooth sailing,

Jim

[Bob_S]

THANK YOU!! to all for your experiences and suggestions - forging ahead.
Fingers crossed we all have a chance to enjoy at least a good part of this season...
My Best to all.
Bob S.

[steve poulin]

I use this zinc on my prop shaft above the propeller. Just fits and gives me a full 7 month New England season. https://www.westmarine.com/buy/sea-shie ... cordNum=11

[appletim1]

What tooling was used to remove the prop. I have a CD27 as well and with the rudder it's really tight.