unsure about what causes this corrosion

[cyrano138]

I looked at a Cape Dory 25d yesterday. In the engine compartment there were four or five bronze through holes with seacocks. They all had this bluish green patina or corrosion or whatever this is. I'm trying to decide whether or not to make an offer and if so how much, and that will depend on how much of a project something like this would be.


The smaller seacock handles turned easily enough but I could not get the larger ones to turn and I didn't want to force it. The wood mounting blocks were a little rotten but I assume they're original and I guess that's not too surprising.



Do they need to be repaired or replaced?

[Scubaseas]

The Spartan Seacocks are easily rebuilt. The other ones are technically not seacocks but ball valves on through hulls. Not that hard of a job to service the Spartans. Re-bedding the through hulls and replacing the wood with Starboard or better G10 or similar is also not that bad of a job if willing to replace the through hull. Just grind the head off. If you need to replace the smaller ones change over to a proper flanged seacock.

Look at the chainplates, especially the bow and sides. They used mild steel backing plates that can be problematic.

[Cheechako]

That is a normal color for bronze.
If you buy you might just redo anything that is marginal, like the blocks on your first haulout.
The bigger ones appear to be tapered seacocks and you just need to get them apart and clean the mating surfaces and lube them. Loosen the nut and washer on one side and give it a good tap, should pop right loose.

Eventually I started using Lanolin for lube on tapered seacocks, it stays good for a long time and completely impervious to water, but the down side is the larger ones do turn slowly in cold water as it's gooey stuff and stays less viscous when cold.

I just clean and lightly sand the surface with 400 grit wet/dry paper by hand to brighten it. I never worried about the "matching" people talk about. They'll never drip with Lanolin.

[cyrano138]

Thank you. What do the larger ones control?

[Scubaseas]

marinehowto.com will be your friend.
Follow the hoses to determine what is what. My guess would be cockpit drains and head outlet for the 1.5" hoses. The smaller 3/4" ones maybe engine raw water and head inlet water.

[skipperpete]

If you do buy the boat, the first job should be a review of the hose clamps in those photo’s, some of em look a bit tired and corroded.

[garyfdl]

I'm gong to pile on and agree with what has already been said. With the ball valves, you can replace them with stainless. Real seacocks would be better. The regular seacock(s) can be rebuilt.

The green is oxide from the copper in the bronze alloy.

There is also something about double hose clamps on through hulls; maybe another member can chime in on that?

[Scubaseas]

Originally Posted by garyfdl

I'm gong to pile on and agree with what has already been said. With the ball valves, you can replace them with stainless. Real seacocks would be better. The regular seacock(s) can be rebuilt.

The green is oxide from the copper in the bronze alloy.

There is also something about double hose clamps on through hulls; maybe another member can chime in on that?

Hoses below the waterline are supposed to be double clamped per ABYC H27.

[garyfdl]

Originally Posted by Scubaseas

Hoses below the waterline are supposed to be double clamped per ABYC H27.

[kapnd]

Originally Posted by garyfdl

I'm gong to pile on and agree with what has already been said. With the ball valves, you can replace them with stainless. Real seacocks would be better. The regular seacock(s) can be rebuilt.

The green is oxide from the copper in the bronze alloy.

There is also something about double hose clamps on through hulls; maybe another member can chime in on that?

Bronze is proper for seacock, never stainless.
The rotten backing sound pretty important to me!

[garyfdl]

Originally Posted by kapnd

Bronze is proper for seacock, never stainless.

Why is that? Please elaborate.

[boatpoker]

Originally Posted by Scubaseas

Hoses below the waterline are supposed to be double clamped per ABYC H27.

My copy does not say that. Can you provide the paragraph number or a screenshot of that.

[boatpoker]

Originally Posted by garyfdl

Why is that? Please elaborate.

Common susceptibility to crevice corrosion and deoxygenation.

[Scubaseas]

Originally Posted by boatpoker

My copy does not say that. Please provide a screenshot of that paragraph.

Going from memory. My copy of ABYC Standards is on the boat which is 2022 miles from where I am.

Might be in P1 which covers engines. If you say it's not in H27 I believe you.

Might be an ISO standard.

[donradcliffe]

I'd be looking hard at that wire which is hose clamped to the thru hull. If there is a difference in the look of the thru hulls with wires and those without, you have a galvanic corrosion problem.

https://www.cruisersforum.com/forums...ls-206199.html