Replace Saildrive Seacock?

[Baddox]

I intend to change our boat's through hull fittings and seacocks this year.  Is it advisable to change the seacock on the Volvo d1-20 saildrive at the same time?  If it needs changing then is it simply a screw-in fitting or does it need thread-lock, PTFE tape or some other magic?

[Yngmar]

Yes, changing it is a good idea. It's a simple BSP 1/2" fitting with a ball valve and hose tail. I would use a permanent adhesive sealant to prevent it loosening or leaking. As it's away from the sun, any PU or MS Polymer adhesive sealant will do.

Be careful when removing the old one. They can snap off, especially if old and a bit weakened from corrosion/dezincifiation. Having to saw the broken stump out of the gearbox housing is annoying! 

I've changed ours to a plastic Tru-Design fitting and ball valve last haulout and seated it with adhesive sealant. That way no further risk of galvanic corrosion (the housing is aluminium and the original fittings brass).

[Baddox]

Thanks.  I intend to replace the other through hull fittings with Trudesign so it's good to know they should work for the engine cooling too.

[Baddox]

Hi Yngmar.  Did you change the "nipple" part 34 in the Volvo parts diag? This would be the equivalent of the through-hull that the valve connects to.

https://www.volvopentashop.com/volspec/en-GB/Details/PentaPartsCatalog/7748570_003?path=MarineDrivesAndTransmissions%2F7748570%2F7748570_44%2F7748570_003

[Yngmar]

Yes. Couldn't find a plastic one I trusted, so I bought a Tru-Design 1/2" BSP through-hull and sawed the long threaded part off, which threads into the gearbox on one end and onto the ball valve on the other. No more corrosion ever again!

[Baddox]

 
I wondered about trying that and using the inside collar nut to gently nip the joint up.  Once lockdown is over and the boat lifted, I’ll give it a go.

[MagicalArmchair]

There is a good video here on replacing the through hull fittings.

https://youtu.be/9bV1rqqvw-k

I want to get this done as all mine are original, and like you I'd prefer composite to make sure it is always sound.

My saildrive seacock is jammed open irritatingly, so I might try and replace that one on haul out on its own. The corrosion around it looks a bit alarming, so I wouldn't be at all surprised if it sheers off. I might try and heat it up first...

[JEN-et-ROSS]

Yes. Couldn't find a plastic one I trusted, so I bought a Tru-Design 1/2" BSP through-hull and sawed the long threaded part off, which threads into the gearbox on one end and onto the ball valve on the other. No more corrosion ever again!

'Yngmar', A wee query.
Our elderly VP 120 still has the original VP seacock, so for years it's been out of sight and out of mind.
So in response to this thread I've obtained a 1/2" BSP Tru-design valve, 90 deg. hose-barb and as you suggested a 1/2"BSP through hull fitting that will have its 'mushroom' removed to fit the VP120......
On assembly, the valve and hose-barb stick out rather a long way, I'm concerned that the engine vibration may, and I emphasise may, put a strain on the apparently very fragile looking 1/2" connection between the gearbox and the valve? Any thoughts?
Another solution may be to fit a 90 deg. hose-barb to the gearbox and a short pipe to the valve. While it would avoid a potential failure due to vibration I can't see a surveyor being very impressed.
So I'm not sure which path to take......Bill.

[Yngmar]

I've shortened the threaded part to as short as I could while still being able to thread on the valve (with the handle removed). Careful when doing this - also have to leave enough room for the handle to swing once installed and space to get to the screw that holds the handle in place.

The fibre reinforced nylon is really quite strong - feel free to test one to breaking load if you got a spare and report back, I'd be curious (breaking load at the hose barb end)! This did concern me a bit, so I made sure the hose has a free run and enough swing room to not apply any force if the engine moves a bunch in case of a collision on the saildrive leg. Not really worried about engine vibration. I wouldn't recommend doing a tarzan swing off the hose, but then I wouldn't recommend that with a metal fitting either, given that my old one (Volvo original, presumably) snapped off flush with the gearbox during removal

If you're really concerned, you  could make up a load bearing collar to strengthen it, but it would be a pretty difficult custom job to fit the uneven shape of the gearbox, and there's only so much space it could rest on. I think if you made a split one with a load bearing collar rotating on a fixed sleeve that sits on the uneven gearbox and presents a straight surface to the collar, it might be possible, but as I said, lot of work!

[JEN-et-ROSS]

Hi Yngmar.
 After I posted the above question a did some trawling and discovered Tru-design do supporting collars that may do the job. (was that the 'collar' you were referring to?)
 I'll check that the surface around the 1/2" BSP drilling on the gearbox is flat otherwise the collar may put an unacceptable lateral load on the connection, although it could be carefully 'trimmed' if there was an issue.
I'll see how I get on.....Bill

https://marinestore.co.uk/Merchant2/graphics/00000002/cu5811n-trudesign-load-bearing-collar_540x338.jpg

[Yngmar]

Yes, I have those on all the hull seacocks, but like I said, you won't easily fit that on the gearbox.

[JEN-et-ROSS]

Yes, I have those on all the hull seacocks, but like I said, you won't easily fit that on the gearbox.

I've been for a look, I see what you mean >:....Bill

[JEN-et-ROSS]

As detailed above, I took the advice of the other members who replaced their old engine seacocks with modern Tru-Design non-degradable ones...
But....
And with boats there always seems to be a 'but'....
Having successfully removed the old one without shearing it off ,as had happened to others, but suffering severe knuckle damage as it was extremely tight and inaccessible..
I fitted the adapted through hull mushroom, (with the 'mushroom removed).....
Then I hit the problem..
We re-engined a few years ago with a nice shiny brand new Beta 30.
The bell-housing and adaptor plate (to permit the marrying of the Beta 30 to the VP 120) sticks out and prevents the fitting of the much, much wider Tru-Design ball-valve......So, I've resorted to fitting a DZR 1/2" 'nipple' and a DZR 1/2" ball-valve.....
So, if you've installed a Beta and married it to a VP saildrive? check that the very large Tru-Design will fit.......c'est la vie......It's a shame as was a very good idea...........Bill

[Baddox]

Update and another BUT!
I replaced the through hull fittings at the last lift-out and intended replacing the sail drive seacock when we were lifted out again today.

The existing seacock is stainless steel; that and the nipple were removed without drama.  The problem started when I  dry fitting the tru-design fitting into the sail drive hole.  The diameter appeared OK and the thread pitch too but the TD fitting would only screw in half a turn before locking up.
It appears that the nipple (Volvo part 3583431) has a tapered thread to match the hole in the SD.  Fortunately the nipple is still in good condition so I’ll refit it tomorrow with some Clesstite thread sealant.  This sealant isn’t recommended for plastic fittings, which isn’t a problem if I’m going back to DZR brass.
 
https://www.yachtboatparts.com/volvo-penta-saildrive-seacock-ball-valve--bronze-dzr-stainless-7204-p.asp