Is your trawler sinking?

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Senior Member
Oct 6, 2007
It may be if you have not checked the bonding system within your boat. Confused? Go to my blog to read my latest post on maintaining your vessel's underwater protection.
Marinetraders article is a good basic.*If a boat is older than 5 years the zinc/bonding loop should be checked to make sure the connections and wire are in good shape as the amount of current is measured in 1/10 of an volt/amp or smaller.* Therefore the connections/wire have to be in good condition to conduct.* So you zincs may look great but the metal on the boat is deteriorating.

*Many zinc loops are daisy chain together in part or whole, so if one connection fails the remainder is un protected.* Many boats have a copper plate tube that runs along the bilge the length of the boat that the zinc/bonding green wire is connected which is better than the daisy chain loop. *If the PMM site come back up there is a recent discussion, Bond though hull or not that is more detailed.

The best advice is to zinc up, and the easiest way is the fish looking zincs that you hang down into the water that you connect to the zinc loop and/or large metal things.* I added three to the Eagle over the winter months.* One connected to the bow thruster which are usually made of different metals be begin with, and the zincs are usually too small.* The second is attached mid way of the zinc/bonding loop.* The third attached to the main engine shaft, plus the external zincs are check every six months.* If you think your zincs are going to fast or you have stray electricity then call a MARINE electrician, not a dirt/domestic electrician.* Best to check, due and trace as much as you can, because they are expensive.**

Oh, galvanic isolators are only good up to 1.2 volts AC anything higher pass though, and/or burn out the diodes so there is no protection.* I think galvanic give false security as many marines reading are higher than that. *Just so you are aware just becaseu your zincs look good and the boat has a galvonic isolator does not mean the boat is protected.* )-;* Arn't boats fun?* )-;

P/F, you are correct about bow thruster zincs being too small. Anyone know where to get some larger ones for a Sidepower?
Try Maybe they can help. I haven't yet tried them myself but spotted a couple specialty ones that I will order next time around.
That's where I get all my zincs. I order 2-3 sets at a time to save on shipping costs. Very happy with them.
Doc, I had a larger zinc thu fitting/bolt installed and connected to the thruster.* I think the reason they go so fast is they are the only zincs in the bow, the main big zincs are in the back and current will follow thru least path of riaiatance, so anything mid way forward would be protect by the tiny bow thruster zincs.*

On the PMM site thee is a long discussion head "To bond thru hulls or not"* I think you posted to it?* Anyway*I scared myself. which I do*all the time,*and rewired/redistributed the zinc/bonding loop.* Tomorrow my diver is going to check the zincs for the winter.* The water is still quite clear.* so I will know tomorrow if there is an improvement.* I will still have him change out the bow thrust zinc one size bigger anyway and have him check/clean every*6 months.

I also added three of the fish type that hang over the side just to be extra safe.* So next time you are out may want to install an additional*bigger separate zinc and/or*add the fish hanging type.****
I have not had the same experience with thruster zincs. They seem to last the same length of time as all the rest. I change them once a year, with quite a bit of life remaining. You might check with a local marine electrician as to what's going on there. I use a "B" bullet shaped shaft end zinc.

-- Edited by Carey at 14:24, 2007-11-03
Trim tab zincs are the first ones to go on my boat....they are usually GONE in about 6-8 months.
I just had as diver check my zincs and the bow thruster zinc 3 clam shell was abut gone in 7 months so put on a 5 clam shell.* The other zincs looked OK. In April I will have him back and in June pull the boat for complete bottom and zincs.* *

I have had several marine electricians on the boat in the last 6 month and tests with in acceptable limits for the marina.* The Everett marine docks are old and have sunk down so that the electrical on many docks is under the water.* Furthermore the commercial dock has not been that well maintained and then there are the commercial boats themselves. *

A large boat uses a lot of high amp items which creates stray AC electricity.* Heaters, stove elements, water heater, battery charger all produce stray electricity. The AC ground is connected to the zinc/loop though the DC negative.* The two biggest anodes that stray electricity can enter the boat are the prop and the bow thrusters. So there are a lot of different factors that can effect how fast the zincs go.

I love my Electro-Guard system with the meters in the salon where I see what's going on with my single sacraficial zinc every time I pass through.
What is the EG System and how does it work?
C lectric, thanks for the tip.**Great prices; I'll do my annual zinc purchase there.

Nice avatar, by the way; kind of scary late at night, though.**
Go2Marine had excellent prices for my zincs, half the price of WestMarine with no sale tax.* Having an aluminum boat, my zincs are pretty pricey, so finding these prices at Go2Marine was good news.
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