PSS dripless shaft seal - raw water pressure question

[svEmerald]

I've installed a PSS dripless shaft seal and need to provide water to it. I can tee it into the engine raw water just after the pump (it's a RWC engine). PSS instructions state a maximum water pressure of 10psi and I'm thinking that the raw water pressure on the A4 doesn't get that high, but wanted to check with the experts! Can anyone confirm?
(I know I can also put it in the output from the manifold but it will be much simpler for me to tee the water line so that's preferred.)
Thanks

[Dave Neptune]

I've played with 3 other than the one I had. All 4 were plumbed right off the pump outlet. Mine was a diesel as were the others.

I don't see how the A-4 would develop any more pressure that those. Someone may chime in that has a pressure gage inline on their A-4. Or call Ken at MMI he is a wealth of knowledge regarding tidbit info regarding the A-4.

Dave Neptune

[Al Schober]

Supplying clean water to the face seal is a good thing. Recommend you take a tap from the water pump outlet. Run it through a filter before going to the seal.
Flow will be miniscule, so any size line will be fine. Depends on what you can find for a filter. 1/8" OD air brake tube is good stuff.

[joe_db]

My PSS does not have water injection, I guess they added that recently.
I do have to bleed it every time I dive on the boat or air can get trapped in it.

[ndutton]

I did this on my previous boat to irrigate the cutlass bearing mounted in the deadwood of a full keel. I suggest tapping into the water system after it passes through the engine so the engine gets full benefit of the raw cooling water first.

The PSS instruction you describe seems to be a departure or progression from the past. At the introduction of dripless seals, no consideration was given to the air pocket that forms inside the seal bellows. When it was learned to be a problem, owners were advised to burp the bellows occasionally by pulling it back from the seal. Then a vent hose was incorporated at the bellows that required its open end to be well above the waterline regardless of engine operation or heel angle. Now it's a positive pressure water injection?

[svEmerald]

Thanks all for the replies.

Just to explain a bit further:
The instructions state that running the hose to a high point is all that is required for boats under 12 knots (which mine most definitely is!) - *except* if there's a bearing in the shaft log. My Cal 34 has a fairly lengthy shaft log with a cutlass bearing at the aft end. That's where the need for the water feed comes from - guess there's not enough flow because of the bearing otherwise?

I'm not able to source the reducer tee I need in time for launch this weekend, so I'll be running it with just a vent hose for the short trip from travelift to slip.

I'll revisit this problem in a couple of weeks, please feel free to continue to offer advice and knowledge!

[ndutton]

Ah yes, Cal 34. Same shaft installation as a full keel boat. The pressurized water injection will benefit the bearing as well as the PSS.

[GregH]

I did this on my previous boat to irrigate the cutlass bearing mounted in the deadwood of a full keel. I suggest tapping into the water system after it passes through the engine so the engine gets full benefit of the raw cooling water first.

The PSS instruction you describe seems to be a departure or progression from the past. At the introduction of dripless seals, no consideration was given to the air pocket that forms inside the seal bellows. When it was learned to be a problem, owners were advised to burp the bellows occasionally by pulling it back from the seal. Then a vent hose was incorporated at the bellows that required its open end to be well above the waterline regardless of engine operation or heel angle. Now it's a positive pressure water injection?

For me on my Alberg 30, the nipple is used to simply vent (hose attached to above the WL). Water comes up through vents in the cutlass bearing assembly and into the PSS. Nice and simple. The docs talk about if you travel over 10kn to have an additional water supply I believe.

[Antibes]

The water injection is not required on a A4 installation. Vent line is all that is needed in boats slower than 12 knots
From installiation instruction online

Low speed boats: (Under 12 knots of boat speed under power and no bearing in the shaft log).

Using a 3/8" (8mm or 9mm) ID "underwater rated" hose (not provided with the PSS), connect the hose to the hose barb fitting installed on the carbon and secure the hose with two (2) hose clamps. Run the hose to a point in the boat at least two (2) feet above the waterline, making sure that the hose does not apply any load on the carbon part of the seal. Keep the hose as close as possible to the vessel's centerline, so the top of the vent hose is never below the waterline, even if the boat heels. Secure the hose in place with the necessary fittings that ensure it will not pull free and drop. This hose is now a venting hose that will help ensure that no air is trapped in the seal.

[svEmerald]

The water injection is not required on a A4 installation. Vent line is all that is needed in boats slower than 12 knots
From installiation instruction online

Low speed boats: (Under 12 knots of boat speed under power and no bearing in the shaft log).

Thanks. However, my boat *does* have a bearing in the shaft log, as I mentioned above - hence the requirement for water feed.