Stern Glands!!!!

[cliffb]

Hi all...
Sorry if this is a stupid question...but I'm new to boat owning...
The Surveyor says that the stern gland needs purging when it next goes in the water. Sounds nasty to me!!!
Questions are:-
What is and where is the stern gland (keep it clean please!)
How do I 'purge' it?

Thanks
Also...while I'm asking
He says the topsides could do with a wax.
Anybody got any views on this? What sort of wax do I use... marine??... car?? Furniture polish!!??

Thanks again.

 

[LORDNELSON]

With regard to the sterngland it seems likely that you have a volvo type dripless seal and all you may have to do is purge (let out) the air trapped behind the rubber seal as soon as the boat is in the water and before you use the engine to turn the propellor shaft.
Opinions vary according about the kind of wax to use. I use car wax but some car waxes contain additives which can cause problems because it makes them difficult to remove. Safest to use a boat wax but usually more expensive.
Since you have paid your surveyor to do a survey he should answer any queries you may have about his report. In particular I should query the purging to make quite sure what he means.

 

[discovery2]

The propeller shaft passes through the stern gland and it is designed to prevent water entering the boat, yet allow the propeller shaft to rotate freely.

Traditionally, watertightness was ensured by 'packing' the stern gland with a mixture of grease and a suitable 'packing' material tightened between two specially shaped 'nuts/collars' through which the shaft passed. Tightening too much caused excessive friction (and heat) on the shaft.

Modern stern glands use different methods, and one method is to use a rubber collar through which the shaft rotates. When the boat is not floating, water drains from the stern tube. When refloated, water refills the stern tube (from outside where the shaft exits the hull/keel) but air gets trapped inside the tube and cannot escape.

Purging the stern gland involves gently squeezing the rubber collar on the inboard end to allow the air to escape. Some water will also enter the bilge, but this serves as an indcation that all the air has escaped. If this is not done, there is a possibility of the (delicate) rubber seals wearing rapidly as no lubricant (water) will be present.

Trust this explanation is reasonably clear!
David.

 

[cliffb]

Thanks David.
The explanation is clear. The action not necessarily so! as I have yet to see this gland. When I next go to the boat I'll have a squint and no doubt all will be clear.
And for a previous poster.... I imagine it will be a Volvo dripless jobby... the engine is a Volvo 2030 ...so I expect so.

Thanks again. So good to be able to ask these inane questions from the anonimity of a Forum... and get good advice! /forums/images/graemlins/grin.gif

 

[tome]

My engine is a V2030, but the gland is a PSS type. With either type, you'll see the rubber bellows around the rear end of the shaft behind the gearbox. Push the bellows backwards until water comes through, then release - job done.

DO NOT use any silicon based polish on your topsides - it will make any future repairs very difficult.

 

[roger]

What happens if you don\'t?

Luckily no personal experience - though I have a seal of this sort. The worry is that the seal when dry will heat up with friction until it melts leaving a big hole.
I have a large notice on the wall by the VHF radio jsut to remind me any everyone else.
The "Roger have you...." from the crew is irritating but might help me avoid a cock-up.

 

[VicMallows]

These seals must be a real pain if you're on a drying mooring, especially as is often the case access is not easy. Glad I've got an old-fashioned packing gland!.

Vic

 

[Mudplugger]

Sorry Vic, Last 15 years on a drying mooring..Soft mud..Knackered the PSS sesal in 2 years, after the 2nd changed to the volvo seal, purged when launching each year, and lasted about 5years each..HTH

 

[jh001ace]

I Have just bought a Benny 331 which had a Volvo 2030, there is a pipe coming off the seal which goes to a seacock, looks like a bit of an odd arrangement, does anyone else have this and should the seacock always be open when the engine is running? There is obviously a seperate seacock for the engine.

 

[discovery2]

I also have this arrangement. The sea cock must be open. As the boat moves forward, water is forced through the pipe to lubricate the stern gear.

Referring back to the original post concerning purging air from the stern gland, this was a time consuming task on my boat, as it involved emptying the contents of the under floor storage, then removing a board covering the shaft. I overcame this by fitting a t-piece in this pipe (from sea cock to stern gland) at the highest point. The branch was then led up into the under floor storage area, terminating in a valve.

When the boat is refloated I open the valve which expels air from the gland and pipe. The tail end of the pipe is of flexible tube than can be lowered to allow and water to flow into a container (or bilge) thus ensuring all air is removed from the pipe. Much easier than delving into the depths of the bilge to perform this task!

I have some images of the setup if anyone wishes to pm me or send an email.

David

 

[tillergirl]

There's a guy in the yard here who is about to fit one of these seals. He keeps his boat on a drying mooring. Does that mean he will have to purge the seal everytime he uses the boat because the water has drained out with the tide?

 

[ex-Gladys]

Not necessarily.. The PSS in high speed version comes with a hose connector. this is used either to cool the thing on 12 knot plus boats, or to use as a breather at lower speeds. That woulds prevent the need to "burp"

 

[tillergirl]

Thanks for that.