Dripless Shaft Seals

Oil Gypsy · 09-14-2020, 10:42 AM

Hello,

I'm just about to haul my boat to change all the thru hull fittings, they are original, 50 years old and in very sad shape.

At the same time Im going to have to change the stern seals, again they are original and in similar condition to the thru hulls. I had to make a temporary repair to one of them when I bought the boat (the auxiliary water inlet was in such poor condition it broke off).

I would be interested in changing to Dripless Seals but as the original shaft seal have the auxiliary cooling inlet (supposedly to provide additional cooling and to ensure the water inside the prop shaft sleeve is changed to stop crevice corrosion) I'm wondering if this upgrade is possible / advisable.

If any other Grand Banks owners have made the conversion could you let me know how it worked out and if the removal of the auxiliary cooling inlet has resulted in cooling issues.

rgano · 09-14-2020, 11:02 AM

I changed my wooden Grand Banks 42 shaft seals from the original greased fittings (I have never seen the type anywhere else) to Lasdrop dripless seals in 1994 and in 2008 upgraded to more robust PYI dripless seals. BOTH had provision for the cooling water input. So I recommend PYI. The 90-degree nipple in your photo appears to be brass which will fall apart in a few years in saltwater. I could not find bronze and so opted for nylon/plastic. You will love the dripless seals.

DDW · 09-14-2020, 11:30 AM

Most dripless will have a provision for water input, and have a barb fitting as part of the kit. The recommendation from Johnson/Duramax (the official "cutlass" bearing) is 2 gallons/minute/inch diameter which is pretty substantial flow.

Oil Gypsy · 09-14-2020, 07:39 PM

Hi Rgano, thanks for the response.

Yes the fitting is brass, but it was only installed as a temporary measure until I could get the boat out of the water to make a permanent repair..

I do have one follow up question, my current shaft fitting fits into a rubber tube installed between the shaft seal and the bronze shaft aperture in the hull. It seems to be about 2.5" in diameter, the current bronze stern seal fits inside the tube (1 male fitting)

With your installation of the PYI dripless seals how was the body of the seal attached to the existing rubber tube. There doesn't seem to be anything on the aft side of the seal to clamp into the tube, did you use a transition piece.

Thanks again.

rgano · 09-14-2020, 08:12 PM

That original rubber boot is replaced by the dripless shaft seal's "bellows which is the transition piece to attach the seal to your shaft log. Take a look at this: https://www.shaftseal.com/pss-type-a-seal.html. That is PYI's explanation of their Packless Shaft Seal (PSS). Here is a photo of my port shaft PYI PSS. Blow it up to see the forward end of the bellows with a hose clamp holding it to the seal. The stainless donut at the very forward end of the system is pressed against the seal pushing the bellows back and inch or so to get the correct pressure. The technical term for this type seal is "face seal" while the Tides system which I have on my current boat in a "lip seal." I think the face seal is the better system and allows for a bit of wiggle in the shaft if it is not perfectly true.

drb1025 · 09-14-2020, 08:15 PM

Is there a strap or something attached to the shaft? Maybe just the angle of the photo.

rgano · 09-14-2020, 10:45 PM

That is the bonding system contact pressing a bronze contact onto the shaft. See the red wire at the lower part of the photo? Should be green, but oh well.

Oil Gypsy · 09-16-2020, 12:50 PM

As an update I got in touch with PYI tech support and confirmed that in order to install the dripless shaft seal I have to remove the rubber extension tube between the shaft aperture and the stern seal. The PSS Dripless seal is supposed to be connected directly to the shaft apertures in the aft cabin / bathroom.

Moonfish · 09-16-2020, 01:57 PM

Our previous boat (a 33' sailboat) had the Norscot dripless shaft seal. Those incorporate a gravity fed tank that drips ATF into the seal to lubricate. We had the boat for 6 years and I topped off the small one-quart ATF tank once (added a couple ounces at most). If I were to upgrade our boat with dripless seals, I'd go with these again.

https://www.ibsenco.com/norscot_shaft_seal/

Slowmo · 09-16-2020, 05:25 PM

Our PYI dripless have a water feed off the raw water system. Keep in mind that dripless seals are not maintenance free and require major servicing (replace bellows) every 6 years. Unlike a conventional packing gland, a dripless seal can fail catastrophically if the bellows fails. If the bellows fails there is a distinct risk of sinking. You also need to make sure nothing gets into the carbon face seal otherwise they can fail. Anyway, be aware that they're not quite as fool proof as a normal packing gland.

sdowney717 · 09-16-2020, 06:46 PM

Just get the GFO marine packing, it makes it dripless using your original flax stuffing box. It also since it is self lubed, needs no extra water input. It is the least dangerous, easiest, cheapest way of going dripless. It is the old adage of KISS.

20 years ago, I put this in, and have had to do nothing to it yet.
2 prop shafts and 2 rudders.

Example
https://www.emarineinc.com/categorie...-Shaft-Packing

**koliver** · 09-16-2020, 08:00 PM

Quote:

Originally Posted by Slowmo

Our PYI dripless have a water feed off the raw water system. Keep in mind that dripless seals are not maintenance free and require major servicing (replace bellows) every 6 years. Unlike a conventional packing gland, a dripless seal can fail catastrophically if the bellows fails. If the bellows fails there is a distinct risk of sinking. You also need to make sure nothing gets into the carbon face seal otherwise they can fail. Anyway, be aware that they're not quite as fool proof as a normal packing gland.

Many have heard this before:
A GB 42 in my YC hit a log in English Bay. The shaft was pulled back by the hit, the dripless then had a 1/2" gap between the faces of the seal. So much water was incoming that the owner opted to beach the boat.

You pay a lot for a dripless. Sometimes too much.

Max Simmons · 09-16-2020, 08:27 PM

I'll second the recommendation of GFO packing. Simple and inexpensive.

Hippocampus · 09-16-2020, 08:58 PM

I put in a retention collar and believe now PSS includes it in their kit. Do you think that would have had any impact on the event you describe?

mvweebles · 09-17-2020, 05:23 AM

I have seen a PSS dripless shaft system fail. It was due to installation error - second set screw stacked stop the first set screw was not installed. It was a breath taking amount of water, but was fixed in less than 5 minutes, plus a hose clamp on the shaft as back up.

The probability of a PSS having a catastrophic failure is extremely low, though impact is admittedly high. Contrast to a traditional stuffing box that often leak causing a wet bilge that masks other problems. Scored shafts are also a common issue as not everyone is diligent about maintenance. I'd say the failure of a traditional stuffing box is fairly frequent, though impact is only moderate-low. Pick your poison.

My general rule: if access to the stuffing box is not good such as many v-drive installations, go with PSS or other dripless. Another good candidate for Dripless are owners who will not or cannot do their own maintenance. Where the stuffing box is reasonably accessible and the owner is okay with regular maintenance checks, the traditional stuffing box with GFO is my preference.

Peter

roddy · 09-19-2020, 12:42 AM

Go with Tides seals...
Have them on our boat, not fool proof, but better designed mouse trap.
https://www.tidesmarine.com/

sbman · 09-21-2020, 01:27 PM

Quote:

Originally Posted by roddy

Go with Tides seals...
Have them on our boat, not fool proof, but better designed mouse trap.
https://www.tidesmarine.com/

Differently designed, but 'better' is not necessarily the case. The Tides seal runs against the shaft which can have it's own problems, each type of shaft seal / stuffing box has it's own peculiarities, leaving it to the end user to decide which they are willing to accept.

psneeld · 09-21-2020, 01:44 PM

Quote:

Originally Posted by sbman

Differently designed, but 'better' is not necessarily the case. The Tides seal runs against the shaft which can have it's own problems, each type of shaft seal / stuffing box has it's own peculiarities, leaving it to the end user to decide which they are willing to accept.

OldDan1943 · 09-21-2020, 02:04 PM

Just my worthless opinion.
If you are going dripless, add a second one as a back up so you dont have to pull the boat out of the water.

Okay, I changed to dripless and in hindsight, if I had it to do over, I wouldn't. I would stay with the original flax type packing. Easier to fix.
So much for my worthless opinion. SHRUG

OldDan1943 · 09-21-2020, 02:07 PM

Just my worthless opinion.
If you are going dripless, add a second one, further up the shaft, as a back up so you dont have to pull the boat out of the water.

Okay, I changed to dripless and in hindsight, if I had it to do over, I wouldn't. I would stay with the original flax type packing. Easier to fix.
So much for my worthless opinion. SHRUG