Removing Seacocks/through hulls that have been glassed in

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Springbok

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Hi, I have a Mitchell 31 which is ashore for winter now and looking to replace my seacocks/through hulls. A couple of them were seized (one is a blakes so that can be easily sorted) Tru design composite would be preference although size/space will probably mean DZR replacements - however on starting to remove them it appears they are glassed in and no apparent sign of any backing nut, so any advice on how to remove these greatly appreciated, most likely they are original from boat build in 1989 🙂
There were also all bonded together, removing this I believe is the best way.
 
Yes, no need to bond them. Even if the through hulls are glassed in you should be able to unscrew the ball valves and replace them if seized, although you may well find you can free them up by cleaning the seaward facing part of the ball. No need to replace the through hulls. The Blakes can be cleaned up without disturbing the body.
 
Tranona said:
Yes, no need to bond them. Even if the through hulls are glassed in you should be able to unscrew the ball valves and replace them if seized, although you may well find you can free them up by cleaning the seaward facing part of the ball. No need to replace the through hulls. The Blakes can be cleaned up without disturbing the body.
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Why is there no need to replace the through hulls, surely these are as likely to be weakened by de-zincification as the valves?
 
johnphilip said:
Why is there no need to replace the through hulls, surely these are as likely to be weakened by de-zincification as the valves?
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No. Because they are almost certainly bronze or DZR. No suggestion the valves are suffering from dezincification - just seized. even brass valves rarely dezincify. Failure is usually the ball or the spindle. The vulnerable areas for dezincification are the threads on fittings, commonly yjr inboard end of a through hull. when he removes the valves it will be obvious if there is any sign but in the period when glassing in was popular brass fittings were not used.
 
Certainly replacing the ball valves and would definitely prefer to change the through hulls although they look fine I guess they are 30+ years old.
Possibly cutting them inside flush with the glassed in backing pads, insert wooden dowel and tap out would be the way to remove them?
 
Springbok said:
Certainly replacing the ball valves and would definitely prefer to change the through hulls although they look fine I guess they are 30+ years old.
Possibly cutting them inside flush with the glassed in backing pads, insert wooden dowel and tap out would be the way to remove them?
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Cut them off flush with the glassed in backing pads, knock a tapered wooden bung in, cut that flush, then cut it all out with a hole saw, the correct size for the new fitting.
 
Springbok said:
Certainly replacing the ball valves and would definitely prefer to change the through hulls although they look fine I guess they are 30+ years old.
Possibly cutting them inside flush with the glassed in backing pads, insert wooden dowel and tap out would be the way to remove them?
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You could - but why? Bronze or DZR will last indefinitely. No benefit from going to all that trouble of grinding them out and replacing.
 
PaulRainbow said:
In post #1 the OP said "Tru design composite would be preference" will they fit the existing through hulls ?
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Yes. They are all the same BSP thread - although no benefit of using plastic rather than DZR from a durability point of view, plus as he says there might be space issues. On the other hand Try Design are less prone to stiffness and potential seizure from non use.
 
Tranona said:
Yes. They are all the same BSP thread - although no benefit of using plastic rather than DZR from a durability point of view, plus as he says there might be space issues. On the other hand Try Design are less prone to stiffness and potential seizure from non use.
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I'd change to composite, i did one heads seacock last time we were out of the water, was a rush job so didn't have time to do the other one. Will do the other one next April when we come out for annual maintenance. I changed the trough hull as well though, the existing one looked OK, but as it was 1988 i changed it anyway. Not easy to be 100% sure of the integrity of the through hull and a new one came with the seacock.
 
PaulRainbow said:
I'd change to composite, i did one heads seacock last time we were out of the water, was a rush job so didn't have time to do the other one. Will do the other one next April when we come out for annual maintenance. I changed the trough hull as well though, the existing one looked OK, but as it was 1988 i changed it anyway. Not easy to be 100% sure of the integrity of the through hull and a new one came with the seacock.
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Clearly that suited you, but there is no rational reason to remove glassed in through hulls not change to composite for durability reasons..
 
Tranona said:
Clearly that suited you, but there is no rational reason to remove glassed in through hulls not change to composite for durability reasons..
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That's your opinion, others are entitles to theirs, but as usual you insist on ramming yours down other peoples throats.

Composite was not much more to buy than DZR, it's what i chose and it's also what the OP wants to fit. As it happens, the through hull, which looked OK snapped off while i was taking it out, so unless you have some sort of X-ray vision it would be foolish not to replace it, especially as a new one comes with the seacock and it takes about 10 minutes to remove the old one, how i described.
 
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