Forums > Sailing General

SD20 seawater cock

Reply
Created by JonE 5 months ago, 18 Jul 2025
JonE
VIC, 536 posts
18 Jul 2025 5:39PM
Thumbs Up

My seawater cock has siezed - like they all do. I want to pull the water pump which is leaking anyway.

Bunnings sell a 1/2" BSP threaded poly pipe plug end. Will this do to plug it while I sort other things out?

I will want PTFE tape yes?

Would love some good advice because i'm going to have water pissing everywhere when I undo the valve so I don't want to have to have half a dozen goes getting it right....!

Ramona
NSW, 7722 posts
18 Jul 2025 6:06PM
Thumbs Up

Have a wooden tapered plug and a hammer handy. That way you wont need it!

garymalmgren
1343 posts
18 Jul 2025 5:20PM
Thumbs Up

Hi Jon.
I take it your plan is to unscrew the cock from the female through hull.
Any chance of diving over and driving in a wooden plug before you start?
Whatever plug you choose you will be trying to fit it and turn the thread against incoming water pressure.
I would do whatever I could to avoid that.

gary

saltiest1
NSW, 2557 posts
18 Jul 2025 7:34PM
Thumbs Up

Yep. Over the side you go with the wooden or rubber plug. The plastic screw on cap will do fine with some teflon tape just be sure not to cross thread. One of my plumbing tricks is to taper the thread tape with only a couple of turns on the first couple of threads and building it up over the next several to make it easier to screw on especially using plastic caps.

JonE
VIC, 536 posts
18 Jul 2025 8:06PM
Thumbs Up

OK it's not a regular thru-hull. It's a 1/2" bsp fitting on the saildrive. The water comes in through the saildrive leg.

I assume that removal is where the risk is? See 58-1 below.

Is it really going to be hard to screw a plastic plug in? I have the hammer and wooden plug ready for emergency...!




Gwarn
245 posts
19 Jul 2025 2:36AM
Thumbs Up

Just pull the hose off the raw water pump and plug it with a wood plug or a nipple with a cap on the threaded side.

woko
NSW, 1745 posts
19 Jul 2025 8:50AM
Thumbs Up

The water pressure is not going to be like a hose on town pressure if that's your concern, but the sight of water freely flowing into your boat does get the heart rate up

saltiest1
NSW, 2557 posts
19 Jul 2025 11:24AM
Thumbs Up

It's only 9.8 Kpa per metre below water surface so inflow is very easily controlled.

JonE
VIC, 536 posts
19 Jul 2025 11:59AM
Thumbs Up

Select to expand quote
Gwarn said..
Just pull the hose off the raw water pump and plug it with a wood plug or a nipple with a cap on the threaded side.


And the winner is..... Gwarn!

OK so in order to do this I would have either had to remove the hose from the tap end or rotate the whole thing with the hose removed from the pump end.

What I did was remove the hose from the water pump end and plug it with... a 1/2 inch drive socket extender with the jubilee clip to seal it off (not much sealing required actually). Then cable tied the end to something above the waterline.

Now I can get the pump off for a service and deal with the siezed CW cock another day.

Thanks all....

grich62
QLD, 672 posts
19 Jul 2025 6:19PM
Thumbs Up

Beaware when you jump in the water to block the inlet SD20 ,s have 2 inlets, one is a hole in the leg and the second is grilled inlet

JonE
VIC, 536 posts
19 Jul 2025 9:05PM
Thumbs Up

Select to expand quote
grich62 said..
Beaware when you jump in the water to block the inlet SD20 ,s have 2 inlets, one is a hole in the leg and the second is grilled inlet


You lot telling me to jump in the water must be up the East Coast.

Down here in Victoria it ain't jump in the water weather

grich62
QLD, 672 posts
20 Jul 2025 3:55PM
Thumbs Up

Select to expand quote
JonE said..

grich62 said..
Beaware when you jump in the water to block the inlet SD20 ,s have 2 inlets, one is a hole in the leg and the second is grilled inlet



You lot telling me to jump in the water must be up the East Coast.

Down here in Victoria it ain't jump in the water weather


It isn't jump in the water here ever because of crocs and sharks or stingers.

JonE
VIC, 536 posts
20 Jul 2025 9:37PM
Thumbs Up

Select to expand quote
grich62 said..

JonE said..


grich62 said..
Beaware when you jump in the water to block the inlet SD20 ,s have 2 inlets, one is a hole in the leg and the second is grilled inlet




You lot telling me to jump in the water must be up the East Coast.

Down here in Victoria it ain't jump in the water weather



It isn't jump in the water here ever because of crocs and sharks or stingers.


Trek
NSW, 1183 posts
23 Jul 2025 9:37AM
Thumbs Up

Is slipping the boat not practical to avoid all the stress and risk?

JonE
VIC, 536 posts
23 Jul 2025 1:14PM
Thumbs Up

Select to expand quote
Trek said..
Is slipping the boat not practical to avoid all the stress and risk?


If I wanted to pay a thousand bucks and wait three weeks. It really wasn't a big deal!

JonE
VIC, 536 posts
23 Jul 2025 1:14PM
Thumbs Up

Select to expand quote
Trek said..
Is slipping the boat not practical to avoid all the stress and risk?


If I wanted to pay a thousand bucks and wait three weeks. It really wasn't a big deal!



Subscribe
Reply

Forums > Sailing General


"SD20 seawater cock" started by JonE