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SailChick20 10-30-2008 11:42 PM

Loose Annode
A couple months ago, I went underwater to pull some weeds wrapped around my propeller. In the process, noticed that my zinc anode was loose and migrating up and down the prop shaft. I went back under with a screwdriver and tried to tighten it, to no just wouldn't. This was also causing a knocking noise while motoring. It will freely move up/down the shaft, but stops about 4 inches from the hull (thankfully!).

I have been told that I should remove it, it's not needed in freshwater...and have been told by others to's a must. :confused:

The manuf. is Martec. This is from their website:

A Martec Bullet Nosed Zinc should be fitted to the shaft precisely leaving a ( 3/8" to 1/4" ) gap between it and the strut to let water thru the strut bearing. The prop should be fitted behind the strut the same way. So instead of three non-streamlined lumps dragging thru the water, you produce one smooth shape including prop, strut, and zinc. When this is not properly done the benefit of any low drag propeller will be severely compromised. All that effort and expense for the ultimate low drag bottom is voided by a poorly placed non-streamlined zinc and a dislocated prop.

My questions:
Do I need this? (assuming to minimize drag through water, and to protect the prop/shaft?)
How can I get the other one off to replace with new?

artbyjody 10-30-2008 11:52 PM

You don't really that kind (looks like it is on backwards to me as well). I doubt it creates that much of a drag. I know on mine - I use the round ones just fine. Its the prop that is the drag and not so much the zinc.

You do need a zinc even in fresh water. They make them specifically for fresh water and are different than the one we use in salt bodies (keep that in mind).

To get the existing one off - Get the right size allen wrench or bit, find a socket that will fit over the end you would turn, put socket on long socket wrench or use extenders - that will give you enough leverage to crank it off.

Otherwise, get the allen type socket that you can put on a drill and try that - it will give you more torque.

Last option - drill out the center of the allen piece of the screw(s)...that will allow you to put a screwdriver into the havles and maybe separate it that way...

Hope that helps...

SailChick20 10-30-2008 11:59 PM

If I can get the screws off...does it come off in two pieces? It looks like one solid piece upon didn't know how to get it off the shaft once I get the screws off.

Here is a pic from the manuf's site...
So what you're saying...should the zinc be between the strut and the prop, not where it is now? Or just turned around the opposite way?

artbyjody 10-31-2008 12:10 AM

1 Attachment(s)
Hope this illustration helps:

Attachment 2607

I annoted where the screws are - it is two separate halves with a bolt securing the halves together.....The round side should be pointing to the keel (if its to be aerodynamic )...

SailChick20 10-31-2008 12:26 AM

lol...LOVE your illustration...thank you! Ok, that makes sense.

I wonder what dumb*ss put it on backwards.

blt2ski 10-31-2008 12:43 AM

The only loose anode on here is Jody's.................ooops..........better shut up while he is still volunteering to crew for me the next three days!:laugher:laugher:laugher:laugher:D:D:D:D

Any way, not to contradict him, but I seem to recall reading that, while you need a "zinc" for freshwater, I am recalling the actual "zincs" do not work as well as another metal, I seem to recall aluminum? or maybe that is the material mix that is special made that Jody is remembering. Hopefully he is not thinking/remembering too much! or he will pull what brain muscle he has in between his ears:rolleyes::rolleyes::rolleyes::rolleyes::laugh er:laugher:laugher:D:D:D:D

Any way.

Need to do some qtly state tax reports for biz, should not be on puter playing, and harrasing Jody!:D:D:D


artbyjody 10-31-2008 12:56 AM


Originally Posted by blt2ski (Post 393471)

Any way, not to contradict him, but I seem to recall reading that, while you need a "zinc" for freshwater, I am recalling the actual "zincs" do not work as well as another metal, I seem to recall aluminum? or maybe that is the material mix that is special made that Jody is remembering.

That's it I am taking the spinnaker position again and seeing how well we can drag it down the hull!

Marty's right - technically - I use the term "zinc" as nomenclature for the anode (its one less syllable)...hence why I stated "fresh water zinc". More or less slang.

To be technically correct: Zinc will not work in fresh water it is purely for salt. Magnesium is the simple answer to your problem with fresh water, although magnesium needs to be removed when going into salt water for long periods.


BTW Marty...

BITE ME! :laugher

sailingdog 10-31-2008 01:16 AM


First, as they've pointed out...the zinc is on backwards... BTW, it does need the 1/4" or so gap between it and the strut or the cutless bearing won't get enough water and can score the propshaft badly.

Second, if you're in fresh water, the zinc should actually be Magnesium or Aluminum, rather than a Zinc. Magnesium is required if you're protecting aluminum parts... like a saildrive or outboard. Aluminum should work in fresh water or brackish water and will out last a Magnesium "zinc", but should not be used if the boat is stored in salt water.

One problem Zinc "zincs" have in fresh water is that they are not as "electrically active" as the magnesium or aluminum "zincs" and if you've got aluminum bits to protect, they will often get attacked before the zinc does—in fresh or brackish water. Also, IIRC, the Zinc "zincs" can get a coating of zinc oxide on them that will essentially insulate them and prevent them from working properly.

There is another good reason to have that bullet zinc on the shaft. If anything happens and the shaft disconnects inside the boat, it can prevent the shaft from pulling out of the stuffing box completely and help prevent your boat from sinking.

When you replace it...remember to seat the zinc firmly with a tap of a hammer. Also, remember to scotchbrite the shaft to get it nice and shiny, so that the zinc makes good contact with it.

blt2ski 10-31-2008 01:33 AM

I would prefer NOT to bite you Jody, as you are the wrong sex jody to be biting IMHO!:eek::rolleyes::laugher

I also knew the actual zinc would not work in fresh water, and aluminum was something to be use, but as you and SD point out, that magnesium is the better choice for a "sacrificial anode" in fresh water. Now say that 20 times really fast!

Ok, time to finish qtrlys, the part I hate about owning ones own business!:hothead:hothead:hothead

see you tomorrow Jody, on H dock, about half way to gas pumps.


sailaway21 10-31-2008 03:18 AM

Once you have the proper sized wrenches/sockets to take it off you may well find that you need a bit of heat. A propane torch used with MAP gas instead of propane will do the trick of heating up those nuts so that they come loose easily.

Once you've got it off you can go home and reward yourself with a nice hot shower and consider the fact that it hasn't been doing anything for quite some time, if ever, in the way of sacrificing itself and yet you have no degradation to your metal fittings. Then you can consider just leaving the thing off like half the other boats in fresh water do. It appears that no sacrifices need be made. (No, I am not a politician!) I would remove it though as it's going to do active harm to your strut at some point.

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