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Prop Strut replacement

supersailor

Contributing Partner
My first Try to get this message through on the site resulted in it suddenly disappearing from the screen. Searching around did not find it. This is the third time this year that this happened.

Those pictures show an awfully large amount of electrolysis on the prop shafts. That is enough to be worrisome. We have "hot" marinas and, I think no truly "cold" marinas. The one I'm in is definitely hot. The source of the stray currents can be other boats or drooping lines under the dock that go underwater. A brand new Westport 120 pulled into a guest dock next to me. Within a short time, the slug of zinc I have on the stern quarter when docked cleared itself of all the marine growth it was sporting. Shortly after, the vinyl covering the grounding cable cleared all the growth also. The lesson here was "It is not only the old wrecks that leak. It can be any boat in the marina.

The very best protection would come from unplugging. Not practical for those of us who insist on having refers, freezers and electric heaters. The attached photo is not of propulsion equipment but of the back of the windlass power switch two weeks after Terra Nova suffered her partial immersion. The side terminal that's almost gone is the hot side. The switch was off so the other side was dead. The difference between the two is sobering. These same forces are at work on your prop, shaft and strut. Because the prop etc. are bronze, they don't get eaten up as fast as the brass does but eaten up they do get.

I use two prop zincs, a zinc slug attached to the negative ground, and a galvanic isolator. The prop zincs used to last about five months, now the look good after a year. Probably it is both the zinc slug and isolator working together that' s doing the trick. Whatever, I'm happy with the results compared to the performance prior to them.P1000490.jpg
 
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Frank Langer

1984 Ericson 30+, Nanaimo, BC
Thanks for the detailed and thoughtful replies. I understand that a galvanic isolator might help minimize electrolysis. Is there any advantage to being in a marina that is equipped with ground fault circuit interruptors (GFCI) to reduce corrosion or do they simply disconnect when there is a wiring problem or short circuit? Put another way, is a marina less hot if equipped with GFCI plug ins on the dock?
So many questions.....
Frank
 

supersailor

Contributing Partner
No, GFCI's do not stop the trickle leaks that wreck props and shafts. The GFCI is there to stop life threatening shocks. The GFCI does not stop small trickles of stray current from affecting the exposed metal. You need a galvanic isolator for that. The cost (about $250) might be a bit of a shocker until you add up the cost of a new prop, shaft and strut. The cheap way, of course, is to unplug and not use 110. Its hard to give up the little luxuries that shore power gives you.

One warning, don't swim in the marina. Several people have died each year swimming. This is especially true in fresh water. All it takes is one boat wiTh bad electricals to do you in.
 

frick

Member III
1971 E29 strut box on hull

IMG_20181018_150511.jpg

This the strut pad on my E29 1971 prepped for the the replacement strut
 

frick

Member III
Photo of strut replacement

Yesterday, while sailing solo in a big blow, my job furler had a major over ride. I could not roll it up.
So I turned on the engine, locked the tiller and went forward to drop the genny.
In the flogging of a 24 knots of wind. The port jib sheet figure eight stopper knot shook out and it sounds up on the prop.
What a rookie mistake for a sailor of 53 years.

I was able to unwind a bunch of the sheet, until I hit a cut in the line.
I could limp back to port at 2 knots.
I went for a swim when I was back in my slip and quickly removed the rest of the rope.
It was very difficult to see under the boat, but it felt like my strut was loose. Crap.

I share more when I get my boat pulled this week.

1971 Ericson 29

RickView attachment 25236
[SUB]IMG_20190111_112622.jpg[/SUB]

My new old stock strut is looking good.
 
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