Something ate away my rudder, thoughts?

[kinnylinny]

Ok, this is gonna be a strange one, desperate for any advice and help as to what it is.

Background. Raw water flow was low. Mechanic suggested I get a scuba diver to see if intake screen was blocked. He dives down and says "totally blocked with some strange white deposits, not barnacles". Then he says "your rudder is gone!" What the heck?!

I will attach photos, but there is white "calcium-like" deposits on intake shield, prop, prop shaft, and where the rudder shaft used to be. He says he's never seen anything like it in 20 years. Wonders if it's an electrical issue that causing it, and maybe the rudder shaft simply dissolves. yet zinc put on 10 months ago shows no deterioration.
Us305 sailboat, 1979, above average condition.

Anyone see/heard of something like this?

[more]

Originally Posted by kinnylinny

Ok, this is gonna be a strange one, desperate for any advice and help as to what it is.

Background. Raw water flow was low. Mechanic suggested I get a scuba diver to see if intake screen was blocked. He dives down and says "totally blocked with some strange white deposits, not barnacles". Then he says "your rudder is gone!" What the heck?!

I will attach photos, but there is white "calcium-like" deposits on intake shield, prop, prop shaft, and where the rudder shaft used to be. He says he's never seen anything like it in 20 years. Wonders if it's an electrical issue that causing it, and maybe the rudder shaft simply dissolves. yet zinc put on 10 months ago shows no deterioration.
Us305 sailboat, 1979, above average condition.

Anyone see/heard of something like this?

electrical issue not first not last and not worst.but if your boat from 1979,hi is redy for recyling or you spend 100-300% more your boat valid

[Searles]

I would say an electrical issue probable DC ,if in a marina and on shore power could be any boat near you ,interesting the visible anodes appear to be ok ,firstly get the vsl out of the water before you have a sinking problem ����⛵️⚓️

[grantmc]

kinnylinny it would be useful for forum members to know where you are.

Your story has been heard/seen before. At least the rudder feel off in the marina and not out on the ocean somewhere.

[kinnylinny]

Originally Posted by grantmc

kinnylinny it would be useful for forum members to know where you are.

Your story has been heard/seen before. At least the rudder feel off in the marina and not out on the ocean somewhere.

So happy this didn't happen while out there, could have been a disaster!

It happened in BC Canada, North Saanich Marina. I'm starting to wonder if the new shore power (2 yrs ago) installed on docks has had some repercussions. Will have to ask around the docks.
Only thing explains it is some sort of electrolysis, but why is zinc perfect? Puzzling to be sure.