Shaft and intake screen zincs

[Traveler 45C]

I know there has got to be a formula somewhere for figuring out the amount of zinc required to protect the shafts. My bottom cleaner installed 2 zincs on each shaft. He says its better but I don’t think so. Is it reasonable to assume that the zincs available from West, designed for 2” shafts, are of adequate size? With only 1 zinc/shaft, they do not get eaten-up quickly.

I do not have sea strainers. I have intake screens. The diver also mentioned that zincs are required for them. I do not remember seeing zincs on them when the boat was hauled for survey. I wouldn’t think that zincs would be required, as they not connected to any other metal. What gives? Are zincs required for the screens?

 

[Genesis]

I have two on each of my shafts. I get six months out of them before I have to change them, and I don't like the idea of changing them in the 50F water in the winter! So I stage the changes to avoid that...

One on each rudder.

The screens may or may not need them. If all that is bonded properly, then they do not need their own protection. But check the bonding system - if its not working right (corroded wires, etc) you can have SEVERE problems with your seacocks and such, which is very bad news if it happens....

 

[67hat34c]

we have a guppy that we throw overboard. we have a fitting in the cocpit that is attached to bonding system. we were loosing zincs every 90d, now we have the same set since september. We also dont have the galvonic isolator installed yet but that is next. There is a meter you can buy that measures galvonic activity and will let you know if you are under or over zinced. I understand that over zincing can cause your bottom paint to fail around the metal fittings.

 

[Traveler 45C]

Genesis,

I remember discussing with you the mounting of a swim deck and the fact that it did not have to be bonded or zinced because it was not in contact with other metals (also no dissimilar metals). Am I to understand that my screens are in contact with the seacocks other than through the water? If they are not in contact with any other metal, don’t the same rules apply as the swim deck?

I’m not as familiar with their construction as I should be.

Anybody know where I can get zincs for these?

 

[Genesis]

They MAY be.

If they are not, then there is no problem.

If they ARE, then there is a problem.

Ditto if they are mounted with a screw or bolt that is not the same metal as the screen is made of. You'd hope that wasn't done, but you might be wrong.

 

[Traveler 45C]

I guess I’ll be in the water this weekend…

 

[Genesis]

Dive dive dive!

 

[OldHatt45]

Traveller45,
I retrofitted my boat with the screens, as I would assume yours is. I through bolted my screens and attached them to the bonding system.

When I bought the screens, I looked around and found the Camp "SZ-1" zincs would fit very nicely on the back of the Screens and still allow the Screen to be pulled off in the event of something happening that required it. All you need do is drill 2 holes on the back of the screen (if memory serves, either 1/4 or 5/16) put a machine screw (philips head) on the outside and nut on the inside. When you do this, MAKE SURE YOU USE LOCK WASHERS on the inside, and a drop of Loctite wouldn't hurt either. Or a "better" solution is to use a Tap on the holes, that way you don't need nuts inside the screens!

Mine have worked nicely. I generally get about a full season out of them.

OldHatt45

 

[Traveler 45C]

OldHatt, do you have the flat screens or the scooper type? Mine are the flat type that are removable.

 

[OldHatt45]

Traveler45C

Mine are the Flat, wedge shaped screen Housing with the removeable screen. Groco If I recall correctly.

OldHatt45

 

[Traveler 45C]

Hmmm…I looked at the Groco web site and I didn’t see the screens that I have. Their flat screen had some kind of door in it. Mine does not. Do yours? What would you use it for?

I spoke with the guys over at Saunders (the yard) this morning. They told me they never heard of using zincs with the screens. Thru-bolting and bonding yes, but zincs? If the entire assembly and hardware are all the same metal and there is no metal-to-metal contact with anything else, I don’t see how a zinc would be required. Were yours getting eaten up without the zincs?

 

[OldHatt45]

Traveler45C

Mine are Buck Algonquin.
Go to http://www.buckalgonquin.com/Buck_Algonquin/Pages/Navigation/Color Catalog705Web.pdf

Very Last Item on Page 18 ;-)
Boy getting old sure S&%$ks. Memory is the second thing to go. lol

I believe these are what you have also.

The Door and/or removable Screen is so that when doing pre-launch stuff you can put bottom paint inside the strainr (Use the Hard paint in there, not the abalative. SOmething like Red Hand (interlux).
Also, should you need to clean stuff out like barnacles that actually grow in there, you can get to the little suckers, by pulling the screen or opening the door. Also should you have a clog you can get under the boat and pull the screen and clean it out.

OldHatt45

 

[Traveler 45C]

And the first?

 

[OldHatt45]

Sorry, can't remember