Rapid Disintegration of Saildrive Leg - SailNet Community
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post #1 of 21 Old 02-08-2020 Thread Starter
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Rapid Disintegration of Saildrive Leg

It didn't look like this three months ago:

https://youtu.be/88ax4YKe9H0
capta and overthehorizon like this.
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post #2 of 21 Old 02-08-2020
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Re: Rapid Disintegration of Saildrive Leg

Looks expen$ive
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post #3 of 21 Old 02-08-2020
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Re: Rapid Disintegration of Saildrive Leg

What do you think is going on. Anodes are still intact. if the starboard anode is 3 months old then it is not working, looks brand new. stray current or ground problem in the marina could be the cause on the left but if so why is the anode not eaten up first. does the boat have Galvanic idolators?

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post #4 of 21 Old 02-12-2020 Thread Starter
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Re: Rapid Disintegration of Saildrive Leg

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What do you think is going on. Anodes are still intact. if the starboard anode is 3 months old then it is not working, looks brand new.
That anode was replaced at the time the video was made.

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stray current or ground problem in the marina could be the cause on the left but if so why is the anode not eaten up first.
Likely a 12-volt issue aboard the boat in question. Definitely electrolytic (stray current) corrosion.

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...does the boat have Galvanic idolators?
No idea.
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post #5 of 21 Old 02-12-2020
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Re: Rapid Disintegration of Saildrive Leg

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Likely a 12-volt issue aboard the boat in question. Definitely electrolytic (stray current) corrosion.


Bingo! A galvanic isolator does not protect from stray DC, especially when it originates on-board....

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post #6 of 21 Old 02-12-2020
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Re: Rapid Disintegration of Saildrive Leg

Volvo or Yanmar? L380's came with both choices. Volvo saildrive is electrically isolated from the engine, while Yanmar is not. An electrical issue on the engine should not effect the Volvo drive, but would have a straight path to water with a Yanmar.

The one weakness with Volvo's isolation approach is that the cooling water is often drawn through the leg, so this could potentially be an electrical path. Changing to a separate intake thruhull prevents this, as well as other issues.

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post #7 of 21 Old 02-14-2020 Thread Starter
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Re: Rapid Disintegration of Saildrive Leg

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Volvo or Yanmar?
Yanmar.
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Re: Rapid Disintegration of Saildrive Leg

Looks even worse than the Volvo sail drive leg I saw on a sloop, on the hard, back in the 80's. Looked like crumbling cheese, sort of.
Did not know the details, but it was in a salt water environment.

It was a sickening sight.

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Re: Rapid Disintegration of Saildrive Leg

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Bingo! A galvanic isolator does not protect from stray DC, especially when it originates on-board....
true but it does protect your anode from being eating up by other boats in the marina and then your saildrive from then being the least noble metal and eaten up by the other boats in the marina. aluminum sail drive makes a great anode for all the other boats in a marina

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post #10 of 21 Old 02-14-2020
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Re: Rapid Disintegration of Saildrive Leg

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true but it does protect your anode from being eating up by other boats in the marina and then your saildrive from then being the least noble metal and eaten up by the other boats in the marina. aluminum sail drive makes a great anode for all the other boats in a marina
Only through DC impressed on the AC circuit. Won't help for galvanic action from a rusting hulk with DC issues next to your boat.

But this is almost certainly a problem on the boat itself. My guess is a wire chafe on the engine harness or alternator/starter wires.

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