stern gear

[colin loach]

Can any help? Vetus stern gear! I have a hose from the prop, going to the top of the weed hatch above the water level, with a stop cock on either end of the hose. When I took the pipe off the top end, I noticed liverpool boats hadn't drilled a hole into the actual weed hatch. There is no way water can flow through the pipe. I don't know how this system is meant to work? I hav e been using the baot for the past 2 years with no ill effect? Is the water mean to flow from the prop out to the weed hatch. Many thanks, colin.

[Mac49]

Can any help? Vetus stern gear! I have a hose from the prop, going to the top of the weed hatch above the water level, with a stop cock on either end of the hose. When I took the pipe off the top end, I noticed liverpool boats hadn't drilled a hole into the actual weed hatch. There is no way water can flow through the pipe. I don't know how this system is meant to work? I hav e been using the baot for the past 2 years with no ill effect? Is the water mean to flow from the prop out to the weed hatch. Many thanks, colin.

 

You can download the instruction manual off the Vetus website, http://www.vetusweb.com/manuals_55.php

I had to because Liverpool boats didn't give me one and were no longer around by the time I needed one.

The one i've got states:

Lubrication

The shaft and if applicable, the rubber outer bearing, gets cooled and lubricated by external water. It is therefore necessary that sufficient external water is supplied whenever the shaft is in operation.

The minimum amount of water required is:

- Propeller shaft diameter 25 mm: 20 litres/hour

- Propeller shaft diameter 30 mm: 30 litres/hour

- Propeller shaft diameter 35 mm: 35 litres/hour

- Propeller shaft diameter 40 mm: 45 litres/hour

- Propeller shaft diameter 45 mm: 60 litres/hour

- Propeller shaft diameter 50 mm: 70 litres/hour

 

You've got me thinking now, I turn the valves on every time I got out but I never thought to actually check the pipe was connected to anything, think i'll go and have a look!

 

Also it might be worth putting some silicon grease in as I got a few drips from mine until I put some in, it didn't appear to have much in (if any) from new.

Rick

 

edit: I get the feeling from reading the instructions that they're designed for faster moving boats than narrow boats so the figures above probably aren't so critical.

Edited August 9, 2009 by Mac49

[colin loach]

You can download the instruction manual off the Vetus website, http://www.vetusweb.com/manuals_55.php

I had to because Liverpool boats didn't give me one and were no longer around by the time I needed one.

The one i've got states:

Lubrication

The shaft and if applicable, the rubber outer bearing, gets cooled and lubricated by external water. It is therefore necessary that sufficient external water is supplied whenever the shaft is in operation.

The minimum amount of water required is:

- Propeller shaft diameter 25 mm: 20 litres/hour

- Propeller shaft diameter 30 mm: 30 litres/hour

- Propeller shaft diameter 35 mm: 35 litres/hour

- Propeller shaft diameter 40 mm: 45 litres/hour

- Propeller shaft diameter 45 mm: 60 litres/hour

- Propeller shaft diameter 50 mm: 70 litres/hour

 

You've got me thinking now, I turn the valves on every time I got out but I never thought to actually check the pipe was connected to anything, think i'll go Let me know what you find I was servicing the engine and knocked the top valve to off by mistake I only noticed there was nowhere for the water to pass through the pipe when I could not find an exit hole in the weed hatch and have a look!

 

Also it might be worth putting some silicon grease in as I got a few drips from mine until I put some in, it didn't appear to have much in (if any) from new.

Rick

 

edit: I get the feeling from reading the instructions that they're designed for faster moving boats than narrow boats so the figures above probably aren't so critical.

 

 

Let me know what you find I was servicing the engine and knocked the top valve to off by mistake I only noticed there was nowhere for the water to pass through the pipe when I could not find an exit hole in the weed hatch

[Les Taylor]

Hi Colin, I have a Liverpool boat with the Vetus watercooled sterngear and it does have a hole through to the weedhatch but it is very difficult to see and cannot be felt with the finger.

My understanding is that the cooling water enters from the sterntube and is expelled via the rubber hose, into the weedhatch.

Have another close look in the weedhatch( maybe use a mirror ) and see if you have a small hole there, it is only about 3 or 4 mm.

 

Les.

[colin loach]

Hi Colin, I have a Liverpool boat with the Vetus watercooled sterngear and it does have a hole through to the weedhatch but it is very difficult to see and cannot be felt with the finger.

My understanding is that the cooling water enters from the sterntube and is expelled via the rubber hose, into the weedhatch.

Have another close look in the weedhatch( maybe use a mirror ) and see if you have a small hole there, it is only about 3 or 4 mm.

 

Les.

Hi Les. thanks for the reply, there is definately no hole, i dont understand how come it has not ceased up. I shall go back to the boat and drill a 4 mil hole at the outlet, the boat was built in 2008 do you think the hole size would be any different to yours. colin

[Albion]

Hi Colin, I have a Liverpool boat with the Vetus watercooled sterngear and it does have a hole through to the weedhatch but it is very difficult to see and cannot be felt with the finger.

My understanding is that the cooling water enters from the sterntube and is expelled via the rubber hose, into the weedhatch.

Have another close look in the weedhatch( maybe use a mirror ) and see if you have a small hole there, it is only about 3 or 4 mm.

 

Les.

 

If the hole is as small as that, and considering that there is nothing in the stern gear to pump water up the tube and into the weed hatch chamber, isn't it more likely that the hose is just an air-release vent to ensure that the bearing and seal face are fully submerged in water at all times rather than sitting in a pocket of air? If it ran dry by sitting in an air pocket then it would surely ruin it very quickly.

Roger

[blackrose]

In the vetus manual it shows either a water scoop skin fitting through which water is drawn up a tube and out of the gland (the opposite direction of flow), or it is shown as part of a pumped system.

When I contacted vetus to ask about the LB setup they said that water could be drawn in through the gland while the boat was stationary (with the shaft revolving) or in reverse, but as soon as the boat went forward water would be going in the wrong direction and wouldn't be drawn in.

I tested it statinary and water came through the gland and I did mean to test it in forward but never got around to it.

 

If you want to test it you'll need two people - one to steer the boat and the other to quickly remove the pipe from the gland and put it back on again to see if water is drawn in. I'd like to know the result but please be careful and watch that spinning sterngear!

Edited August 9, 2009 by blackrose

[colin loach]

In the vetus manual it shows either a water scoop skin fitting through which water is drawn up a tube and out of the gland (the opposite direction of flow), or it is shown as part of a pumped system.

When I contacted vetus to ask about the LB setup they said that water could be drawn in through the gland while the boat was stationary (with the shaft revolving) or in reverse, but as soon as the boat went forward water would be going in the wrong direction and wouldn't be drawn in.

I tested it statinary and water came through the gland and I did mean to test it in forward but never got around to it.

 

If you want to test it you'll need two people - one to steer the boat and the other to quickly remove the pipe from the gland and put it back on again to see if water is drawn in. I'd like to know the result but please be careful and watch that spinning sterngear!

when you tested the gland did water go out though the weed hatch, and what size hole have you got

 

If the hole is as small as that, and considering that there is nothing in the stern gear to pump water up the tube and into the weed hatch chamber, isn't it more likely that the hose is just an air-release vent to ensure that the bearing and seal face are fully submerged in water at all times rather than sitting in a pocket of air? If it ran dry by sitting in an air pocket then it would surely ruin it very quickly.

Roger

Roger i have been out on the boat for the last year even on the thames, surley it would off gone wrong by now. do you think that although there is no way for air or water to pass though the sterntube there as been enough water seaping in to stop it from going wrong.

[blackrose]

when you tested the gland did water go out though the weed hatch, and what size hole have you got

From memory the hole in the weedhatch is about 6 - 8mm diameter but I wasn't able to see if the water was expelled through the weedhatch with the shaft spinning for obvious reasons!

I just took the pipe off the gland and tested it - first in neutral (no water coming through), and then in gear with the shaft spinning (water coming through). I assumed the water would be expelled through the weedhatch once the pipe was reconnected?

If you've got a pipe fitting connected to the weedhatch (above the waterline), why don't you just drill it through?

Edited August 9, 2009 by blackrose

[colin loach]

From memory the hole in the weedhatch is about 6 - 8mm diameter but I wasn't able to see if the water was expelled through the weedhatch with the shaft spinning for obvious reasons!

I just took the pipe off the gland and tested it - first in neutral (no water coming through), and then in forward with the shaft spinning (water coming through). I assumed the water was expelled through the weedhatch.

If you've got a pipe fitting connected to the weedhatch (above the waterline), why don't you just drill it through?

yes that is what iam going to do. thanks to all for your help. Colin.

[blackrose]

yes that is what iam going to do. thanks to all for your help. Colin.

Be sure to wash any swarf out of the fitting before reconnecting the pipe. You don't want that in your sterngland.

Although having said that there's little to stop any other crap from the canal getting in there.

[colin loach]

just one thought, if when going foward the water could be sucked out of the sterntube, but this may not hasppen if the hose going into the weed hatch is blocked off. yes or no?

[blackrose]

just one thought, if when going foward the water could be sucked out of the sterntube, but this may not hasppen if the hose going into the weed hatch is blocked off. yes or no?

Possibly when moving forward the water flows in the opposite direction (in through the weedhatch and out through the gland), so in your case the gland wouldn't have been lubricated.

As I said, with the boat moored up and in forward gear the water flowed in through the gland and out of the hose fitting leading to the weedhatch, but vetus said this wouldn't happen if the boat was moving forward.

So according to vetus, NONE of the water lubricated sternglands fitted by LB will work as intended! I really need to test the theory for myself.

[Albion]

when you tested the gland did water go out though the weed hatch, and what size hole have you got

 

 

Roger i have been out on the boat for the last year even on the thames, surley it would off gone wrong by now. do you think that although there is no way for air or water to pass though the sterntube there as been enough water seaping in to stop it from going wrong.

 

Colin, I think you misunderstand me. I was supporting the fact that there was likely to be a hole there, albeit a very small one (you only need a very small bleed hole for air but you need a much larger hole for water flow), because otherwise if any air was trapped permanently you would have ruined the bearing, or at least the gland seal. If you truly have no hole in the connection through the plate then there is no way for the air to get out (except if the hose isn't secured in an air tight way) and there is risk of running the gland face seal dry, in my humble opinion. On my new barge I am having a water lubricated two cutlass bearing and one face seal system. The difference is that on my boat the filtered water is positively fed by a tapping off the raw water cooling system for the engine. The bearings etc are always under positive pump pressure, whereas I think yours will be under negative pressure for the reasons that I describe below.

 

 

just one thought, if when going foward the water could be sucked out of the sterntube, but this may not hasppen if the hose going into the weed hatch is blocked off. yes or no?

 

Vetus have already alluded to the fact that you are only really going to get a positive flow to the bearings when going astern. When in ahead, ie most of the time, the prop pulls water past the swim and expels it rearwards. In this case there has to be a slight negative pressure at the tip of the swim because the water isn't flowing to the prop as fast as the prop would like it to be supplied to it. This negative pressure is what makes the stern of a boat sit down in the water when you are travelling forwards. The more restricted and shallower the channel the more the effect is noticeable because of the difficulty of getting the water past the boat and to the

prop efficiently.

 

Now, what does worry me slightly is that this negative pressure will surely try to draw water through the tube that is connected to an air pocket in the top of the weed hatch upstand. The way the Vetus system seems to be designed is to use a scoop, forward facing into the flow, that creates a postive feed pressure. My gut engineering feel is that I would rather see the supply tube and fitting situated below the water line somewhere where it can draw a water supply if there is a negative pressure in the bearings and stern tube. Or, an extension to the tube fitting mounted in the weed hatch lid that enters the water just below the uxter plate and turns slightly forward (bit like an aeroplane pitot tube for speed instrumentation). But this system will feed silt laden water to the bearings and all the more so on shallow, narrow canal channels.

Of ourse, the other possibility is that I'm barking up the wrong tree and have completely misunderstood how this system is supposed to work on an LB narrow boat which is always possible.

Roger

[Iain_S]

Colin, I think you misunderstand me. I was supporting the fact that there was likely to be a hole there, albeit a very small one (you only need a very small bleed hole for air but you need a much larger hole for water flow), because otherwise if any air was trapped permanently you would have ruined the bearing, or at least the gland seal. If you truly have no hole in the connection through the plate then there is no way for the air to get out (except if the hose isn't secured in an air tight way) and there is risk of running the gland face seal dry, in my humble opinion.

(Big Snip)

 

On Gamebird, we have a similar type of arangement on the stern tube, but do not have any hose connection leading to the weedhatch (or anywhere else). I think most, if not all, Sea Otters are the same.

 

The only thing we have to do with it is after launching, when the rubber cover is pulled back until water dribbles from the seal. This would tend to support the theory that the hole is an air bleed, rather than a water exhaust.

Iain

[david and julie]

On Gamebird, we have a similar type of arangement on the stern tube, but do not have any hose connection leading to the weedhatch (or anywhere else). I think most, if not all, Sea Otters are the same.

 

The only thing we have to do with it is after launching, when the rubber cover is pulled back until water dribbles from the seal. This would tend to support the theory that the hole is an air bleed, rather than a water exhaust.

Iain

From your description that sounds like the Volvo type, I have one on my Piper built boat which has the Volvo emblem on the rubber boot. I believe that Volvo sell a grease(Silicon?) which you're supposed to squeeze into the seal occasionally. Don't ask me how though.

 

There's a bit of info about them near the bottom of this page.

http://www.pelaginox.com/data/d-driveline1.html

[blackrose]

From your description that sounds like the Volvo type, I have one on my Piper built boat which has the Volvo emblem on the rubber boot. I believe that Volvo sell a grease(Silicon?) which you're supposed to squeeze into the seal occasionally. Don't ask me how though.

 

There's a bit of info about them near the bottom of this page.

http://www.pelaginox.com/data/d-driveline1.html

The vetus model is also supposed to have a blob of silicon grease inserted into a hole which is accessed by undoing a small stainless allen bolt on top of the gland, just in front of the pipe that goes to the weedhatch. I think its supposed to be done annually

Edited August 9, 2009 by blackrose

[colin loach]

what a lot to think about, I will phone Liverpool boats today, although they not good at given answers to questions once they have sold the boat.

[ChrisPy]

what a lot to think about, I will phone Liverpool boats today, although they not good at given answers to questions once they have sold the boat.

they are not good at after sales service anyway if they are out of business.

let me know if they answer the phone ...............

Edited August 10, 2009 by ChrisPy

[ChrisPy]

In the vetus manual it shows either a water scoop skin fitting through which water is drawn up a tube and out of the gland (the opposite direction of flow), or it is shown as part of a pumped system.

When I contacted vetus to ask about the LB setup they said that water could be drawn in through the gland while the boat was stationary (with the shaft revolving) or in reverse, but as soon as the boat went forward water would be going in the wrong direction and wouldn't be drawn in.

I tested it statinary and water came through the gland and I did mean to test it in forward but never got around to it.

 

If you want to test it you'll need two people - one to steer the boat and the other to quickly remove the pipe from the gland and put it back on again to see if water is drawn in. I'd like to know the result but please be careful and watch that spinning sterngear!

Mike, Vetus drawing shows the hose connection as the 'Water Inlet'.

I suppose in the LB set-up we must assume that there is some pressure generated in the weedhatch, forcing water through the hose to the gland.

[mayalld]

Mike, Vetus drawing shows the hose connection as the 'Water Inlet'.

I suppose in the LB set-up we must assume that there is some pressure generated in the weedhatch, forcing water through the hose to the gland.

 

Yes, that is correct!

 

We have a similar arrangement, which relies on splash water from the prop onto the cavitation plate.

 

5 years old, and silicone greased through the appropriate hole every 2 years.

 

Not a drip as yet.

[Albion]

Mike, Vetus drawing shows the hose connection as the 'Water Inlet'.

I suppose in the LB set-up we must assume that there is some pressure generated in the weedhatch, forcing water through the hose to the gland.

 

It is tempting to think that but there are two arguments why I don't think that is the case:-

1. If you want the flow of water to be sufficient to lubricate the stern gear bearing/seal why make the hole in the lid of the weed hatch so small?

2. On a properly designed weed hatch there is a baffle plate fitted in the aperture in the uxter plate, even when the seal is at the top of the weed hatch up-stand) to prevent splashing and noise from the prop. The prop is the only thing that could generate the pressure that you suggest and yet it is (should be) baffled to prevent that.

I know some builders didn't use a baffle plate and LB may have been one of them.

 

There is another possibility, of course, and that is that LB didn't really know what they were doing at all and simply found somewhere to stick a pipe that they had to attach to the stub on the bearing to prevent leakage. There may be no more science in it than that.

Roger

[ChrisPy]

2. On a properly designed weed hatch there is a baffle plate fitted in the aperture in the uxter plate, even when the seal is at the top of the weed hatch up-stand) to prevent splashing and noise from the prop. The prop is the only thing that could generate the pressure that you suggest and yet it is (should be) baffled to prevent that.

You will soon find there is pressure if you could remove the hatch cover leaving the lower plate in place!

 

Why is it called a cavitation plate? Cavitation is a very special phenomenum involving air coming out of solution under extremes of low pressure within the water, usually only occurring at high revs on high speed vessels.

Cavitation is not the same thing as drawing air into the prop area.

 

The lower plate prevents turbulence, but it does not cancel the pressure generated around the periphery of the prop.

[colin loach]

I have just phoned Liverpool boats but they are not accepting phone calls. I have had no luck trying to speak to a technical person from vetus. dose anyone know the phone number of vetus in England.

[nb Innisfree]

Why is it called a cavitation plate? Cavitation is a very special phenomenum involving air coming out of solution under extremes of low pressure within the water, usually only occurring at high revs on high speed vessels.

Cavitation is not the same thing as drawing air into the prop area.

 

Sorry if it sounds bit nit picking but cavitation produces steam bubbles which condense and leave a vacuum which then collapses, no air coming out of solution.