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Question about strut zincs

Frank Langer

1984 Ericson 30+, Nanaimo, BC
Hi,
There have recently been several posts about corrosion in struts, with owners recommending addition of zincs on the strut.

I asked our boat yard staff about this, and they said that as long as zincs on the prop shaft are maintained its not necessary. Furthermore, they said that drilling a hole through the strut to bolt a zinc on either side unnecessarily weakens the strut.

It seems to me that the strut is separated from the prop shaft by the cutless bearing, though I guess there still could be corrosion from the stainless steel bolts holding the strut in place from inside the hull.

Can someone provide a convincing reason to either add a zinc to the strut, or not? Any wisdom on this is much appreciated. ☺️

Frank
 

footrope

Contributing Partner
Blogs Author
I would add one. You're right about the insulation of the strut due to the cutless bearing. It is a little tricky to get the pancake zincs to fit nicely to the curved strut, but as long as the strut surface is clean it will work. My strut zinc lasts longer than the prop or shaft zincs, about twice as long. But it still is being eaten away and thus is doing something. I keep my boat plugged in to shore power at the dock, so keeping up with the zincs is at least a once per year job. My current and last marinas were fairly good electrically. The hole isn't going to affect the strength enough to matter. I don't believe that there was any factory electrical bonding of the strut where it is embedded into the hull.

20161130_Prop-and-Shaft-before-small.jpg
 

Kevin A Wright

Member III
I never had a problem on my E27 for the first 10 years in my moorage. I always dove myself to clean the bottom and replace the zincs so got a very good look at things and I used two zincs on the shaft. Then one day the strut started turning pink and pitting. But still no problem on the prop or shaft. I can only assume someone moved into the area with a 'hot' boat leaking voltage into the water. I quickly drilled a hole through the strut for a pancake zinc. No problems for the next 15 years.

Again, cheap insurance and the tiny hole in the strut won't hurt anything. You probably will also need to grind flats on the strut so the zinc is well grounded.

Kevin Wright
E35 Hydro Therapy
 

Kenneth K

1985 32-3, Puget Sound
Blogs Author
I added strut zincs last year upon advice from my marina haul-out crew. They advised removing the copper-based anti-fouling paint (bottom paint) and adding a zinc to the strut. I added two small zincs rather than one large one. I felt the smaller discs made better contact with the curved surface of the strut, and I mounted them aft where the foil is flattest. While drilling through the strut, I was surprised how thick the bronze was (thicker than it looks)--I had no worry at all about weakening the strut by drilling two small holes. I did not paint the strut under the area of the zincs.

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