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Old 02-03-2017, 12:26 PM   #7
City: North Charleston, SC
Country: USA
Join Date: Sep 2010
Posts: 4,385
Originally Posted by sdowney717 View Post
Our summer water temps can get into upper 80's.

Have not checked any anodes. There are 4 under there.
I am also wondering about switching to aluminum anodes.

I always have replaced them at haul outs, and typically my hauls are on a 4 year schedule.
Typically, the rudder anodes are there but wasted, and the shaft anodes loose or gone as in completely missing.

What I have done with the underwater metals on my last haul in 2014.
I first paint with zinc chromate primer all the running gear.
Then I coated - smeared a thin layer of a waterproof polyurethane over all except the shaft.
I used Loctite S30 polyurethane. It is smooth enough to cover with a thin layer.

Then bottom paint all of it.

My thinking is keep the water away from the metal and the chance for corrosion goes way down. I don't ever see any metal disintegration-pinking etc...

Another thing I wonder is, barnacles have bases they attach to metal. Those bases keep the metal dry away from salt water, so barnacle bases may actually help preserve the metal.

A prop edge, the barnacles get worn away, so prop edges can dezincify I suppose easier as they are exposed to the salt water..

So I am curious how the zincs are doing this time.
I think you are making a lot of mistakes here. First, don't put copper based bottom paint on metal running gear. A coat of polyurethane isn't going to protect it. If you want to paint your running gear, use paint designed for running gear.

Your anodes should not be "wasted" when you check them. There should still be 1/3 to 1/2 of the metal left when you replace them. Anodes are far cheaper than props and shafts.

Barnacles do not protect underwater metal.

You would do well to hire a professional boat diver to maintain your boat's hull and running gear. I can't tell you how often to have this done because it varies with the climate and conditions. Divers in your area will know how often it should be done and of course, you can ask slip neighbors or the marina manager. Just as a point of reference, in my area, it's every couple months in the winter and as often as every three weeks in the summer.

Your diver will inspect your anodes and replace them as necessary.

You might be able to reach the same speed with a fouled bottom as with a clean one but you will be using a lot more fuel to do so. I always make a call to have mine done immediately before leaving on a cruise.
rwidman is offline   Reply With Quote