corrosion devise

[jzlatar]

Just a simple question: I’ve a 30’what devise I should install to avoid corrosion and where, ej:engine, shaft etc.
Thanks in advance
Jorge -Genesis-

[Bermuda]

Jorge-
I am afraid your question is not "just a simple question", certainly there is not a simple answer.

Basically for most boats you will need a shaft zinc and you might need zinc anodes for your engine depending on the manufacturer and model.

Typically other metal items below the waterline and not part of the bonding system may need some sort of sacrificial zinc.

My anwers are far from definitive, personally if I didnt know what was required on my or any particular boat, I would have a experienced marine mechanical/electrical technician take a look and make a determination.

Shooting from the hip where bonding and sacrificial zincs are concerned can lead to catastrophic failure of items like engines, shafts, shaft logs, etc..


bruce@boatskipper.com

[hamiam]

With all due respect to Bruce, there are many simple and cheap ways to isolate your boat galvanically. I dont claim that this is an end-all, be-all list but its a good start:

1. Depending on the amount of room you have 1-2 zincs on your prop shaft. They must make an electrical connection to the shaft so dont paint the shaft in the area where you put them on and dont paint the zincs themselves.

2. Engine Zincs. Depending on the make and model of the engine you may have one or more zinc pencils that need to be 50% or more.

3. Drivesaver device. Its primary purpose is to absorb vibration and shock but it also prevents electrolysis of your engine by blocking the current from the water from ever reaching your engine.

4. Galvanic isolator. If you keep your boat on a dock and are plugged into shore power this is a must; otherwise your boat can turn into an electrolysis magnet from the stray currents.

5. Have not tried this one myself but, using a length of copper wire connect all of your sources of underwater metal (ie seacocks) and then attach to that one of those sacrificial "grouper" (basically just a zinc but its shaped into a fish for some reason) and throw said grouper into the water.

One of the major magazines had an article on this very subject recently. You might want to try a google search.


Regards

MJH

[jzlatar]

Mamiam. Thanks for your response, I’m following the advise, I started with have 1- zincs on the prop shaft,I will try to install it this weekend the only thing is that I will try to do it while the boat is in the water. Any suggestions on the right way to do it? Y know that the shaft must be free of paint, grease or any other material, should I use sand paper before the installation? I know that after tighten the bolts I should tap it with a hammer for proper sitting and then retighten it up again, do I mist something?
Regarding ” the engine Zincs. Depending on the make and model of the engine you may have one or more zinc pencils that need to be 50% or more”, what do you mean by this?.
As you can see, I,m a new starter and there is a lot of things that the books don''t tell you.
regards
jz - genesis

[hamiam]

For the shaft zincs: The idea is that you have an electrical connection between the zinc and the shaft. I would not advise using sandpaper on a stainless steel shaft as this may lead to a rust problem down the line. I would use something like a scotch-brite pad to remove any growth, paint, etc before attaching the zinc(s).

For the engine zincs (if you have any): Much like shaft zincs they are sacrificial. IE they are made to corrode so that the engine doesnt. Some engine manufacturers recommend that you replace the engine zincs once a year or when they have deteriorated to 50% of their original weight or size. You need to find our from the manufacturer if you have engine zincs, where they are located, and where you can order replacements.

Good luck.

HAM