Zincs- Need advice

[moguls2go]

Hey fellas-

Over the past few years I've been installing 2 shaft zincs per side in the spring and am lucky to have them all by the fall. Not because they're worn out... because they somehow fall off.

How am I screwing up this installation that seems so simple? I tighten the 4 allen screws as evenly as possible and then torque them as much as I can. And yet.... there's a case of disappearing shaft zincs.

Help!

[Ironworker]

Locktite (get the removable stuff)

[Carl]

...what Rick said.

I also like to use B&S Zincs, heavier duty and they use real nice size bolts you can really crank on, not like those Camp ones. Even with the HD ones I cannot say I haven't heard a zinc hit the wheel when cruising. Quite a distinctive sound of metal hitting metal.

[moguls2go]

Awesome, thanks guys!

[Amberjack]

Did it yesterday on Amberjack for the 26th year. My first year the yard installed the zincs, next spring we found one of them had slid down the shaft and was riding in front of the cutlass bearing. Bad deal. So I asked around and was fortunate to get good advice early in my B31 career.

The shafts spin at 2,300 rpm so the forces are huge.

Polish the shafts to remove the old accretion.
Put a dab of Locktite on the threads as advised above on this thread.
I put a dab of Locktite on the inside of each zinc to help prevent spinning though I don't know if it makes any difference.
After the zincs are in place and initially tightened tap tap tap with a hammer, then take up the slack. Don't be afraid to whack the zinc. Rotate the shaft to the other side of the zinc and tap tap tap again. Repeat until the screws don't take up anymore, perhaps 4-5 times. You'll be surprised at how much you can tighten up.

[Stephan]

Don't be afraid to whack the zinc.

This.
Once they are set on the shafts by a few good whacks to each side I have found the bolts require additional tightening.

[Tony Meola]

I do the same thing, hit it with a hammer a few times and spin them and hit them again.

Only time I ever lost one was when the area around the screw eroded away. We knew when it happened since we heard it hit the hull. Never had one slide down the shaft.

[Yannis]

My yard guys don't use locktite.
They just tap tap tap and take the slack.
Never lost a zinc.

[Raybo Marine NY]

im not saying people dont do it- but ive never seen locktite applied in a yard
the shaft zincs have a big tag on them that tells you to smack them with a hammer

first a piece of emory, get the shaft nice and clean 360 degrees
install zinc gradually tightening the bolts so they are even, smack, rotate, smack, tighten again. I do this 3 times.

[Carl]

I am very reluctant to suggest tapping anything, never mind "whacking and smacking"...although your right, that is the way to install.


I've told the story of fitting a coupling that gets lightly tapped onto a shaft and showing the customer how to install and remove....easily with a couple taps of a mallet of the wooden portion of a hammer. The following day the shaft comes back with threads a 1/4" shorter; he decided to "tap" the shaft into the coupling from the tail end...with a sledge.

I agreed with loctite as some people have an odd sense of what tighten the bolts means.

[Amberjack]

Thinking about it, shaft collar zinc design doesn't appear to have changed much in the last 50 or so years when most shafts probably turned at <1,000 rpms. With modern diesel engines mine turn 2300 rpm at cruise and 2500 rpm at WOT. We must be operating at the outer design limits of this type of zinc.

[Ironworker]

Which brings up a dang good question. I've always used Zinc anodes but it appears the latest recommendation is to use Aluminum anodes. I'm an old dog so I'm sticking with Zinc but what is the opinion of others on this issue.

[Raybo Marine NY]

regarding engine RPM, there have been higher revving gas inboards as long as diesels

[Amberjack]

Which brings up a dang good question. I've always used Zinc anodes but it appears the latest recommendation is to use Aluminum anodes. I'm an old dog so I'm sticking with Zinc but what is the opinion of others on this issue.

Aluminum anodes are recommended especially for fresh water. I’m in fresh water 6 months and salt water 6 months so a couple years ago I tried aluminum. They were really “hot” so I went back to zinc.

[Dug]

So, I used to use two zincs per shaft and invariably they would loosen due to their intended purpose. The galvanic corrosion ate metal and it would loosen and then as many here have described, slide down the shaft. Bad primarily because once loose it didn’t provide protection any longer. Fast forward and I discovered Godfrey zincs which have a bronze core ring and they are awesome. Never once do they loosen. Contact as well as fit is maintained by said bronze inner ring and I only use one per shaft now. I buy them from New England Propeller. Doug Peck knows me by now. I’ve even been known to pick them up for a buddy down in Rye, NY as his harbor has awful electrical issues and his zincs go faster than a Tesla Plaid.

https://godfreyboatzincs.com/

https://neprop.com/marine-engine-parts- ... n-collars/

I swear by them. Big difference maker.

Dug

[Dug]

Also, always whack the zincs as you tighten. Always. This is to ensure a good fit and even contact with the shaft.

[scenarioL113]

I have never "whacked" a zinc in my life....until today. All this talk has me overthinking it....

[Ironworker]

I know a little about things that spin and harmonic balance. It would seem to me that placement of a zinc on the shaft would have some effect on the balance and tune of the shaft. I do know that vibration is bad. Zincs are certainly not machined to be balanced. This thread has me thinking that placing the closer to the strut would help with some of the vibration.

Also are there better quality zincs, i.e. some that are more balanced? I'm going to do some research into the zincs that Dug recommends.

[lobsta1]

I used to use Godfrey zincs. Then I had one that after an entire year in the water it still looked brand new. Then I hauled & next year put it on the opposite shaft. End of that season it STILL looked brand new. Threw it away & stopped using Godfrey.
Al

[Carl]

My understanding is the quality of the zinc has to do with its composition and the way it’s made.

Pure zinc is not good and too far from pure is not too good….it’s the 3 bear and Goldylox story. Too pure and the crust up too fast creating a layer of insulation. If they do not corrode fast enough the juice goes someplace else eating something aside from the sacrificial metal.

How it’s made is also something. Die cast are less porous, less surface area. Cast are supposedly more porous offering more surface area. There are also forged zincs…I’m not sure what that benefit is, but know they are pricey.


I believe zinc in fresh water forms an insulating crust making them less sacrificial….I believe that’s why if fresh weather aluminum is used.

We make pure iron anodes for a customer and aluminum boats I believe use magnesium…grab a stack of 1-1/2x6x 12 plates like they are nothing. The new guys think they are zinc…which 4 require some effort

In any case,There’s a ton of different anodes for different purposes. I however don’t really know what they are. I just make em or sell em to spec.

[Amberjack]

I know a little about things that spin and harmonic balance. It would seem to me that placement of a zinc on the shaft would have some effect on the balance and tune of the shaft. I do know that vibration is bad. Zincs are certainly not machined to be balanced. This thread has me thinking that placing the closer to the strut would help with some of the vibration.

Rick-Factor into the equation that (I’m told) zincs need to be separated 10-12” from the strut to allow for clear unimpeded water flow to the cutlass bearing.

Hey Max, are you getting enough response to your zinc question? Sometimes it’s like trying to take a sip of water from a fire hose when asking advice on this forum.

[Dug]

Al, thats unfortunate. Perfection is an impossibility for any manufacturer. I would likely have called and asked for a replacement and offered the one in question back to them so they could look into it from their end and possibly solve a problem they didn’t know they had.

I’ve never had that problem with any zinc, regardless of brand. Sorry to hear you did.

Regardless, the Godfrey’s have worked flawlessly for me, and one less thing to worry about on a boat is good in my book!!

[Tooeez]

Ironworker is right about the balance. I once had one shaft that suddenly developed a substantial vibration without hitting anything or any other warning. I thought I might have wrapped a plastic bag around the wheel, but when I dove under the boat I discovered a chunk missing from one side of the zinc on that shaft. I doubt if the missing piece weighed half an once, but that was the cause of the vibration.
Also, IMHO, if the zincs aren't eroding away (and getting loose in the process) they aren't doing their job

[Rawleigh]

I usually use two per shaft, spaced fore and aft, a foot or so from the strut and the stuffing box. I figured putting it in the middle was asking for imbalance. I always whack the zincs on both sides and tighten at least twice. Camp zincs with he little bronze balls instruct you to do that. I have never lost one until it disintegrated on its own.