Zinc and my hull.

id. painter · 11-11-2003, 08:37 AM

I have a metal hull . I want to keep the salt from hurting it.
How many zincs? where on the boat? and how to attach? Any help will be great.
Should I be concerned about it, with about 20 salt days per year? Thanks. id. painter

fish assassin · 11-11-2003, 09:19 AM

ALWAYS be concerned about it!! (IMHO) You can add zincs to your boat by dropping
"zinc birds" overboard or by welding tabs on your boat to attach them. I have four
zinc plates that are bolted into tabs at the stern of my 30 footer and that seems to
work pretty good. If you have flow-thru fish boxes that are not painted on the
inside, just placing a couple zinc bars on the floor (where they make contact with
bare metal) will help keep the corrosion out of the boxes.

Your outdrives/outboard lower units should have zincs already attached to them.
Figure out where they are and keep an eye on them. When any of your zincs are 50%
used up, replace em!

Best thing to do to assure that you don't have electrolisis issues is to stay
unpluged from shore power. If you have a bad ground on the shore power (VERY common)
you will eat the zincs off your boat very quickly.

If you are just going to be a day boat and take your boat out of the water after
use every day, zincs are not as important. Just make sure that the ones on the
outdrives are in good shape and wash the boat down good with fresh water after *each
and every* use.

Hope this helps ...

-assAssin-

id. painter · 11-11-2003, 09:39 AM

Thanks F. Assassin. I will mostly be pulling my boat each day, but ,there will be times that the boat stays in the salt for maybe a week at a time.
Do the zinc bars need to be distributed around the hull or will a couple at stern be O.K.? Thanks id. painter

fish assassin · 11-11-2003, 10:01 AM

I don't want to steer you wrong on this issue ... it's just too important!! All
I can do is give you MY experience ... I have a 30' aluminum boat. The only place
that my boat has zinc on it is at the stern and a couple of chunks I threw in the
bottom of my fish boxes. The hull seems to be holding up well now that I have stayed
unplugged from shore power. I had some serious problems before I figured out that shore
power can (and lots of times IS) a problem.

If you are only leaving your boat in the water for short periods of time, it might
do you well to look into the "zinc birds". Most marine supply houses have them.
They are a fairly stout piece of zinc that attaches to your boat with a
piece of wire. You just need to attach to someplace where the metal has no paint.

If your boat is not painted either inside OR out, I have been told that you can just
slap some zinc in the bilge on the floor someplace where water collects. For zinc to
work it needs to make contact with the salt water.

Now you know as much as I do!! Even though I have been studying this issue for the
last two years, it sure seems to me to be something akin to Black Magic!!

:grin:

-assAssin-

id. painter · 11-11-2003, 10:51 AM

Thanks much . I will have some on my boat this summer. I was surprised at how much the zinc bars on the motor have been eaten in the 20 or so salt days this year. Thanks again . id. p.

HOGGEMIN · 11-12-2003, 08:44 AM

I have a 20' Motion Marine and they use 15lbs on there boats and on the 24' they add 2 more small ones on the keel towards the bow. Also disimular metals cause electrolis, use nylon button washers on every screw or bolt.

id. painter · 11-12-2003, 09:42 AM

Thanks Hoggman. Tell me a bit more about the zincs and the positionong on the craft.
When you say 15 lbs , how many bars are you talking about. ect.... Thanks id. p.

id. painter · 11-12-2003, 09:48 AM

Oops ,,, Hoggemin.

HOGGEMIN · 11-12-2003, 09:51 AM

Howdy id. painter it was good meeting you at the TA meeting last friday. I have a outback model so the motor is mostly behind the transome. You can go to Motion Marine's web site, but I can't give you a link,they arn't sponcers. I have a 5 lb zink in my motor box, and 2 5 lbers, one on each outside of my outback motor box. I hope this helps more than it confuses you.

Have a great day

id. painter · 11-12-2003, 10:07 AM

Thanks , it was great to meet you as well.
I do think it is helping . I have a good spot for a big zinc on the stern ,, on the plate you would put your transducer, my boat has two.
I can also put one back by the bildge, inside.
But, I dont see many places that look like it will go easily,without drilling or welding on the hull its self. Thanks much. id. painter

Pitch Pocket · 11-12-2003, 12:29 PM

The amount of zinc needed depends on the marina you moor the boat in. Some are hotter than others. Unless you're a chemical engineer, it is figured mostly by trial and error. If you check your zincs after after a season (or a couple of months) and they look like they are corroding and plenty of zinc is still there, then the zinc is doing it's job and you're ok. If they are totally eaten up, then you need more zinc (surface area is the key) to keep up with the galvanic action. They should be welded to the hull, or bolted to stainless studs welded to the hull. You have to have a good connection and zincs with cast in mounting straps are better than those drilled for bolts.

If you only have it in the salt for 20 days per year, I doubt you'll have a big problem.

By the way, you have to make sure you don't use zinc anodes on the hull if you have aluminum/indium alloy or magnesium anodes on the drive. The aluminum alloy/magnesium anodes will protect the zinc (less noble than zinc). Check with your engine manufacturer to find out what they use.

[ 11-12-2003, 01:43 PM: Message edited by: Pitch Pocket ]

fish assassin · 11-13-2003, 04:47 AM

Pitch Pocket,

OK, you just answered a question I have had for quite a while ... I'm still
learning!!

Any idea where you can get the aluminum alloy "blocks" or "bricks" to put
on the hull? I've been using zinc and have noticed that the anodes on the
outdrives are getting worked a lot harder than the pure zinc on the hull. Any
help you might be able to offer will be *greatly* appreciated!!

Thanks,
-assAssin-

Pitch Pocket · 11-13-2003, 07:22 AM

Can't remember the name of the place, but the company that sells the wobblers on Swan Island has all kinds of anodes in the back and I'd bet Englands can get whatever you need.

I think most drive makers use the aluminum alloy, but you should check to make sure. Magnesium is the least noble of the lot and if they use magnesium, you should match it.

id. painter · 11-13-2003, 07:26 AM

Thanks P.P. It sounds like I have a whole bunch of learning to do about this. What you said makes sense, sort of , mostly, yah , O.K. Thanks again. Welded ... id. painter

Pitch Pocket · 11-13-2003, 08:54 AM

id.....if you have any specific questions, I'll try to clarify it for you. Shoot me an email if you want.

id. painter · 11-13-2003, 09:11 AM

At this point I think Im too ignorant to ask any specifics. I will read some about the process and then maybe I can converse better on the subject. Must learn more. id. painter