Old stern gland still installed with new PSS seal

[WaldPinkler]

There's still the old stern gland installed with a plugged up hose hanging off it.

I don't know if it's correct or if I have to remove it at some stage. Any advice?

What can I do with the old tubing hanging around?

[stormalong]

Don't know why you are calling it a stern gland. There is no packing nut. Looks more like a shaft log with a water fitting. Is there a cutlass bearing inside it? Could the water fitting be there to cool & lubricate the cutlass bearing?

[WaldPinkler]

Ok, I don't know what it is. Just guessing. There's a hose/tube behind that. The hose coming off it is disconnected, probably at the time when the PSS was installed.

[Uncle Bob]

Originally Posted by WaldPinkler

Ok, I don't know what it is. Just guessing. There's a hose/tube behind that. The hose coming off it is disconnected, probably at the time when the PSS was installed.

To me it looks like a stern gland fitting with the nut and presumably the packing removed and the pss clamped to the threaded section. The hose nipple should have been removed and replaced with a suitable plug threaded in, not done as you describe, however as is it will not cause any major problems provided that it is not damaged. I wouldn't make any major changes, just inspect regularly.

[Scubaseas]

Looks OK. As long as they removed the shaft log and packing. If water gushes out if you remove the forward hose (back one) you're good to go.

[grantmc]

Originally Posted by stormalong

Don't know why you are calling it a stern gland. There is no packing nut. Looks more like a shaft log with a water fitting. Is there a cutlass bearing inside it? Could the water fitting be there to cool & lubricate the cutlass bearing?

OK I am asking on behalf of all the forum member who don't want to demonstrate their nautical knowledge ignorance. So this thread can become, I hope, an extended learning opportunity.

What is the difference between a stern gland and a cutlass bearing?
What jobs do they do and are they ever together, or is one it system or the other?
Is there a third alternative, and of so what?

[stormalong]

A stern gland has packing in it to prevent water flow into the boat. Typically the packing is compressed by a packing nut that is adjusted to allow a slight leak when the shaft is rotating. The leak, a few drops per minute is there to cool and lubricate the packing.

A shaft log or stern tube is a pipe through which a shaft passes from inside to outside of the boat. Attached to it is some kind of seal to prevent water inflow. Commonly called a stern gland but there are more modern types from various manufacturers that work better. An example is the Packless Sealing System (PSS) shown in the first post picture.

A cutlass bearing is a rubber bearing that the shaft rides in outside of the boat. It is water lubricated and can be mounted on a separate strut or on full keel boats it is in the shaft log. It must be water lubricated or it will quickly wear out. If mounted directly in the shaft log there must be some provision to get water to the front of it.

[Boatyarddog]

Originally Posted by WaldPinkler

There's still the old stern gland installed with a plugged up hose hanging off it.

I don't know if it's correct or if I have to remove it at some stage. Any advice?

What can I do with the old tubing hanging around?

That's a shaftlog bearing support,this is nessessary to support the forward part of the shaft.
It's fine as is.
I'd hook the hose back up to a water feed, although most bellows on dripless systems are "Burped"
Boatyarddog

[Boatyarddog]

Originally Posted by grantmc

OK I am asking on behalf of all the forum member who don't want to demonstrate their nautical knowledge ignorance. So this thread can become, I hope, an extended learning opportunity.

What is the difference between a stern gland and a cutlass bearing?
What jobs do they do and are they ever together, or is one it system or the other?
Is there a third alternative, and of so what?

Great question: without citing texts.

A Stern Gland is attached to the shaft log in order to support the shaft end coming into the boat, and to allow a threaded fitting for the packing and packing nut to be attached to.

A cutlass bearing is a shell of metal/rubber inserted into a strut fixture or even a stern gland in trawlers to support the prop shaft alignment into the boat.

Stern glands and cutlass bearings do work together.
Alternatives are outboards, and out drives, jet drives.
Sails......
Boatyarddog

[mlydon]

Guys, you’re slightly wrong - a packing glad doesn’t support the prop shaft AT ALL. The shaft should be well clear of everything except the packing. The engine supports the inboard end, and should be adjusted so that the shaft travels through the stern tube dead-center. The interior of the PSS does have a bearing surface, but it’s purpose is to keep the PSS centered on the shaft, not to support the shaft.

The cutlass bearing at the outside end of the stern tube, or on a strut, supports the prop end.

An xtremely long, or high-torque prop shaft might have an intermediate bearing.



Matt

[Boatyarddog]

Originally Posted by mlydon

Guys, you’re slightly wrong - a packing glad doesn’t support the prop shaft AT ALL. The shaft should be well clear of everything except the packing. The engine supports the inboard end, and should be adjusted so that the shaft travels through the stern tube dead-center. The interior of the PSS does have a bearing surface, but it’s purpose is to keep the PSS centered on the shaft, not to support the shaft.

The cutlass bearing at the outside end of the stern tube, or on a strut, supports the prop end.

An xtremely long, or high-torque prop shaft might have an intermediate bearing.



Matt

One end of the prop is supported by the strut and cutlass, the other is supported or suspended by the stern gland and gear alignment to the stern gland and dripless or packing whatever system is used.
It's a fluid connection, the trans coupler and cutlass are the alignment for the prop shaft, thru the log, the dripless is the seal.
Boatyarddog

[nuku34]

Boatyarddog:
Sorry, but I think mlydon is correct.

To give a complete overview:
The prop shaft goes through the stern tube. The outboard end (the one with the prop attached) of the prop shaft is supported, and centred in the outboard end of stern tube, by a rubber water-lubricated cutlass bearing which can be located either in the end of the stern tube or on a separate strut.

OK, the inboard end of the propshaft is connected to, supported by, (and centred in the inboard end of the stern tube) by either the engine/transmission or by a separate hard-mounted thrust bearing assembly like an Aquadrive unit. The propshaft must be centred in the stern tube and not touching it!
Since the stern tube is open to the water at its outboard end (even with a cutlass bearing installed directly in the tube since the cutlass bearing has grooves to let water in for lubrication), there must be a seal on the inboard end of the stern tube to keep the water out of the boat. The only purpose of the seal to keep water out, it is not there to support/centre the propshaft in the stern tube! If this was not the case then why are 99% of packing glands and 100% of dripless seals mounted on a short flexible rubber hose which is attached to the inboard end of the stern tube? The reason for this is because in the real world, propshafts don't end up exactly in the centre of the stern tube and are not perfectly straight. The rubber hose allows the seal to "float" with the shaft, but NOT support it.


Engine alignment is the process by which you move the engine/transmission on its mounts so that the propshaft is 1) perfectly centred in the inboard end of the stern tube, and 2) the transmission flange is perfectly at a 90 degree angle to the prop shaft (to prevent the shaft being bent).
I'm very happy if anyone has a comment or critique to the above description...

[RaymondR]

High speed vessels sometimes have a water feed to the cutless bearing to prevent them running dry and hat at high speed.

[Searles]

Guess I will wade in on this one,most are partly correct ,in our neck of the woods ,yes the cutless bearing if used maybe in the skeg if so the recommended length is a min of 4 shaft diameters ,there may also be a bearing in the aft end of the sterntube usually half the length of the skeg bearing ,also on the inside of the stern tube a short bearing maybe fitted in the sterntube ,these three bearings centre the shaft in the hull ,a stuff box or pss type seal water lubricated next in line , the shaft coupling with or without a flexible link to the g/ box , just how it should be done.⛵️⚓️

[Boatyarddog]

Originally Posted by stormalong

Don't know why you are calling it a stern gland. There is no packing nut. Looks more like a shaft log with a water fitting. Is there a cutlass bearing inside it? Could the water fitting be there to cool & lubricate the cutlass bearing?

This is a bulkhead mounted stern gland, there is no flexibility in this arrangement, and the shaft is supported by the trans coupler here.

The threads for the packing nut would be under the bellows, it would otherwise act just the same as a shaft log with a hose and packing gland.

You would see this arrangement on trawlers, or bigger craft.

The hose should be connected to a raw water source to aid in lubrication, although water pressure will do this for you.

It's best to "burp" the bellows of air pockets.
Boatyarddog