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Celestialsailor · 10-09-2011, 22:01

I figure this is about as good a place as any to post this question

I have been "donated" some Stainless Steel ball valves with Teflon seats for my under the waterline cockpit drains of my boat. My old ones were gate valves

. So I would be threading them onto bronze thru-hulls. I would be bonding them to an external zinc. My thinking is they will be fine as good quality bronze ball valves have stainless balls. I read an earlier thread regarding Buck Algonquin valves made in China where the chrome plating on the brass ball corroded away. These SS valves are USA.
Anybody done this?

S/V Alchemy · 11-09-2011, 08:15

The bronze valves have SS balls largely encased in a Delrin or similar sphere for slipperiness. Whether the isolating plastic is carried through (via a bushing) to the handle is not known to me, but you need to figure out the galvanic action aspect of the various metals, as bonding seems a particularly contentious area of debate.

Would SS be as "noble" as bronze?

Celestialsailor · 11-09-2011, 08:19

Quote:

Originally Posted by S/V Alchemy

The bronze valves have SS balls largely encased in a Delrin or similar sphere for slipperiness. Whether the isolating plastic is carried through (via a bushing) to the handle is not known to me, but you need to figure out the galvanic action aspect of the various metals, as bonding seems a particularly contentious area of debate.

Would SS be as "noble" as bronze?

Another way to look at it is to campare it to the SS prop shaft with a bronze prop. That set up uses a zinc. It's getting harder to find an all bronze ball valve these days.

**David M** · 11-09-2011, 08:20

Silicon bronze is not very reactive with stainless. I have seen many applications where they are attached to each other in salt water with no electrolysis. Ideally you would want silicon bronze thru-hull valves.

vintageray · 11-09-2011, 08:32

I had something pretty weird happen. My stainless shaft was badly corroded where it exits the cutlass bearing. Had a deep groove half way around it, looked as though cut with a torch. Zinc was gone, prop was fine. Had to have a new shaft made. By the way, anyone know why they also put a zinc on the shaft between the coupling and the stuffing box on lots of boats. There's no water there and if there were, corrosion would be the least of your worries.

donradcliffe · 11-09-2011, 08:35

See galvanic chart and discussion in Metals in a Marine Environment

Celestialsailor · 11-09-2011, 08:56

Quote:

Originally Posted by vintageray

I had something pretty weird happen. My stainless shaft was badly corroded where it exits the cutlass bearing. Had a deep groove half way around it, looked as though cut with a torch. Zinc was gone, prop was fine. Had to have a new shaft made. By the way, anyone know why they also put a zinc on the shaft between the coupling and the stuffing box on lots of boats. There's no water there and if there were, corrosion would be the least of your worries.

That's interesting because I just had the opposite situation. I just purchased this boat and the zincs had long gone. The shaft was perfect and when I grabbed the prop to break the nut loose, it crumbled in my hand.

**David M** · 11-09-2011, 09:00

Nice explanation donrad.

**James S** · 11-09-2011, 09:38

Quote:

Originally Posted by vintageray

By the way, anyone know why they also put a zinc on the shaft between the coupling and the stuffing box on lots of boats. There's no water there and if there were, corrosion would be the least of your worries.

Its a good place to keep the spares and at the same time if placed properly can act as a stop to keep the shaft from backing out if a flange failure occurs.

Cheechako · 11-09-2011, 09:55

Quote:

Originally Posted by vintageray

I had something pretty weird happen. My stainless shaft was badly corroded where it exits the cutlass bearing. Had a deep groove half way around it, looked as though cut with a torch. Zinc was gone, prop was fine. Had to have a new shaft made. By the way, anyone know why they also put a zinc on the shaft between the coupling and the stuffing box on lots of boats. There's no water there and if there were, corrosion would be the least of your worries.

It's likely from the boat sitting, but usually it would be inside the cutlass bearing. I have seen the area inside there look like worms crawled around and ate grooves in it.... from sitting and oxygen depletion on the stainless. The worst thing you dan do to a boat or diesl engine is NOT use it.
"By the way, anyone know why they also put a zinc on the shaft between the coupling and the stuffing box on lots of boats. "
to keep the shaft from going to the bottom if it comes loose from the coupling is the reason i usually do it!

HopCar · 11-09-2011, 14:39

I don't think you'll have a problem using the Stainless Ball Valves if the grade of stainless is meant for use with salt water. It's not uncommon to see bronze underwater fittings fastened with stainless bolts. Groco and Apollo both make stainless ball valves for saltwater use. One thing you can do to improve the set up would be to use a Groco IBVF Flange Valve Adapter. There are two problems screwing a ball valve directly on a thru-hull fitting. The first problem is that a Thru-Hull fitting has straight threads and a ball valve has tapered threads. You can not get good thread engagement with this set up. The second problem is that there is no flange to support the thru-hull which can break off without support. That's why real seacocks have flanges that fasten to the hull. The Groco IBVF solves both of these problems and makes it easy to replace the valve if it should fail in the future. Here is a link where you can order them:
Groco Flanged Adapter IBVF
Following is a picture of how it is used.

osirissail · 11-09-2011, 18:36

Quote:

Originally Posted by vintageray

. . . By the way, anyone know why they also put a zinc on the shaft between the coupling and the stuffing box on lots of boats. There's no water there and if there were, corrosion would be the least of your worries.

- - There are different grades of stainless steel available for propeller shafts, you may have had a very low grade one.
As Cheechako said - It is there as a safety "stop" to keep the prop shaft and propeller from leaving the boat should the prop shaft separate from the transmission flange. It is just cheaper and easier to use a "zinc" than something else.

SkiprJohn · 11-09-2011, 20:18

Aloha Martin,
I'd use 'em.

Cheechako · 12-09-2011, 09:04

Quote:

Originally Posted by HopCar

I don't think you'll have a problem using the Stainless Ball Valves if the grade of stainless is meant for use with salt water. It's not uncommon to see bronze underwater fittings fastened with stainless bolts. Groco and Apollo both make stainless ball valves for saltwater use. One thing you can do to improve the set up would be to use a Groco IBVF Flange Valve Adapter. There are two problems screwing a ball valve directly on a thru-hull fitting. The first problem is that a Thru-Hull fitting has straight threads and a ball valve has tapered threads. You can not get good thread engagement with this set up. The second problem is that there is no flange to support the thru-hull which can break off without support. That's why real seacocks have flanges that fasten to the hull. The Groco IBVF solves both of these problems and makes it easy to replace the valve if it should fail in the future. Here is a link where you can order them:
Groco Flanged Adapter IBVF
Following is a picture of how it is used.

Good informative Post!