Shaft Zinc Placement

[John F.]

I was told or read that I should put the shaft zincs about 6" or so up from the strut. I was looking at it today, and was wondering if the zinc would disturb water flow to the prop, whether that's where they're supposed to go, etc. In walking around the yard looking at other boats, the zincs were anywhere from centered between the hull and strut or down towards the strut.

Where are the zincs supposed to go?

Thanks-

John F.

[Sean B]

I'm not sure it really matters, except that you really don't want it slipping down and stopping water flow to your cutlass bearing, which will burn it up. Some guys put a hose clamp on the prop-side of the zinc to keep it from doing that. I used to center mine on the shafts.

After I realized that they would sling off after only a month or two (I used camp zincs and I put them on right, but they would always fly off anyway) and then had one ding my prop on it's way off from the boat... I added a transom zinc and quit using the shaft zincs completly.

[Kevin]

I was told better to put them as far away from strut as possible. Water turbulence was the reason. Mine are about three quarters the way up the shaft. Not sure if a donut zinc causes much turbulence to begin with.

[Charlie J]

i have transom, rudder and shaft zincs, two on each shaft, i dont think it realy matters were you put them. mine are appox a ft away from the struts for the first pair and appox a ft to the next set. sean i would not leave the shafts unprocted and rely on the transom zincs alone, the more the better

[Brewster Minton]

CJW is right. Put zincs on everything. I have 2 on each shaft, rudders, trimtabs and a large plate, plus on the strainers. I pull the boat half way through the season and replace all. Just how I do it. Do not know about how far from the strut they should be. Mine are 1/2 way.

[Tommy]

We mounted our shaft zincs forward as close to the hull as possible to cause the least amount of turbulence to the props. We have strut, rudder, and trim tab zincs as well.

Tommy

[Sean B]

sean i would not leave the shafts unprocted and rely on the transom zincs alone, the more the better

I completely re-ran the entire bonding system with all new wiring a couple of years ago. About six months ago I suspected a stray current problem and I re-checked the hell out of everything then too. When considering leaving the shaft zincs off, I checked the electrical (bonding system) connections between the shafts and the big transom zinc I added to the boat. There is a really good connection between the two, even without having shaft brushes. I've got a braided bronze grounding wires between the shaft coupler and the gear coupler, and that must be where I get the good connection. Also checked the corrosion potential / zinc protection of the shafts with a silver/silver chloride anode and they're good. So, I think I beat that issue to death and I am comfortable without the shaft zincs.

I've also got zincs on my rudders and trim tabs, and also on the three braces for the swim platform, and of course the big square transom zinc that is bonded to everything. I'm pretty zincked up:



Am I the only one who looses shaft zincs within a few months of installing them?

[Carl]

I'd spend a few bucks more and go with B&S Brand Zincs. Camp are better then nothing but u get what you pay for.

[Charlie J]

ill see how good the shaft zincs stay on, boat is going in in a few weeks and then coming out at the end of may begining of june for some work.

[RussP]

when installing shaft zinks you have to set them with a hammer after inital tightening. There is a little circle outside which sits above the little anode, give it few shots with a lump hammer on each side and retighten. You should never have a zink slip down the shaft if installed properly.

RussP

[Rawleigh]

I've never had one slide. Usually when properly installed as Russ said over freshly sanded shaft, they "glue" themselves on as they corrode. I've seen them hang on with just one screw! Of course I have also seen them gone entirely, but the corroded spot where they were indicated they went down fighting!

[John F.]

Thanks for all the advice. I'll try to move the zincs up the shaft a bit. My boat sits at my dock behind my house, and I don't keep plugged into shore power. My zincs (American-made) usually are at most about 25% gone by the end of the season.

John F.

[Rawleigh]

Sean: I've been thinking about adding a transom zinc. Any tips or pointers you can think of that would help, like sizing, etc.

[Sean B]

I did the hammer bit on the shaft zincs and I'd still loose them. Not sure why noone else seems to have this problem.

Rawleigh,

It is an easy upgrade. I installed stainless steel rods with fender washers and nuts on either side of the hull, with 5200 sandwiched in bewteen. This was a mistake, should have used silicone bronze. No ill effects as of yet after 2 years, but if I had it to do over again (I may just do it anyway) I would the SiBr bolts.

Then leave enough of the stud sticking out to add the zinc and another nut to hold it on, and enough on the inside to add the wires and their nuts. The transom zincs (sometimes called diver zincs) have a few different sizes, I just picked one in the middle range without much consideration. You can actually find in Nigel Calder's book a way to estimate how much zinc you should have hanging on your boat, but it seems like voodoo science to me. Whatever you do, test the corrosion potential before and after, only way to tell. You can actually over-zinc too so it's worth testing periodically.

After you get the zinc installed, you have to run BIG wires to your copper bonding strips. I ran one gauge 2 wire (about 1/4" diameter + insulation) from each zinc lug to each copper bonding strip, using hard-soldered end lugs, shrink wrap, penetrox, tinned wire...the whole works. I had my genny out at the time and wouldn't have been able to access the area if I hadn't, something to consider. I also made a 2 gauge jumper and tied the two new zinc lugs together, effectively connecting the port and starboard bonding strips together. Bertram had done that with one 8 gauge wire (too small) at the rear, and there was a fair amount of resistance between them away from the transom before I did that. I also tied them together at midships too but I was getting a little nutty about it at the time, not sure if all that was necessary.

Also with the transom zinc in service, I noticed that it likes to scum up occasionally, especially in the summer. Being in FL may be the reason, you may never have the problem in VA. If you do, wire brush it clean every month or so.

More about the testing of your zinc protection here: Corrosion Testing

[Charlie J]

dean
i to do the hammer thing, but still come up short somtimes, either eaten
up or spun off

[dougl33]

I use the camp zincs with the "hammer' method. 2 on each shaft. While I've never lost a zinc I have had them eat away.

[ed c.]

I use the Tony Athens method, best of all breeds.very good article in Bd.com archives

[Mikey]

Rawleigh,
Getting ready to install transom zincs, have all the stuff.
Come on down, I'll show you what I'm doing.

[Rawleigh]

Cool Mikey!! Give me a call when you are headed that way!

[Matt29]

Ed C,
Can you elaborate on the method you use? I didn't realize that there was a much different method than was previously discussed.
Thanks,
Matt

[Dug]

I have always put them about a foot up the shaft from the strut.

I used to lose them all the time. Then I switched to another brand from what all of you have mentioned and it has a brass or copper ring inside the zinc. They are called Godfrey. The fastening is done by that ring, and it also serves to provide contact to the shaft. They haven't fallen off for 3 years and that is how long I have used them. They are simply put awesome! They are a bit more expensive, but they last.

I buy them from NE propeller every spring at the NE boatshow. I actually went from 4 on the shafts this year to only two total because they were staying on all summer long. This has increased the effectiveness and saved some money in a safe and good way.

I do the hammer smack etc, and it works great with a good zinc. The problem I had with all the others was that the fasteners all held in place in the zinc. And it always seemed that was the first part of the zinc to get eaten. So they inevitably fell off due to that more than the overall zinc being eaten.

I say try the Godfreys. You will think they are much better. I have found a world of difference with them staying on.

Remember, you want your zincs to be used up. It only idicates a problem if they go much faster than usual or much slower. If they are going slower, pay attention to other things that may be going instead. If they suddenly start going quickly, I look for new boats in the area, or I think then that something might be amiss on my own boat. That is when the fun begins...

But I really do think quite highly of the Godfrey zincs.

[Capt Dick Dean]

Sean, it looks to me that you painted the rudders and then installed the zincs. I would never do that - I put the zincs on right to the bear metal and then paint around them. Like everyone else, have them on the rudders, shafts and trim tabs.
And another thing. I don't buy the ones made in Canada. They don't work good.

[Sean B]

No it's just a good paint job- bare metal under the zincs

[ed c.]

I hammer the hell out of them, they never fall off. I put 2 on each shaft, 1 about 6" from the strut, and one about 8" from the hull. I also use shaft brushes.