Shaft seal water feed

maej

maej

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Tides marine insist their seal needs a minimum of 4 litres a minute flow rate of coolant water... That sounds like an awful lot of cooling water to take away from a rubber exhaust hose that relies on the flow of engine coolant to cool and muffle the exhaust gas.

Am I worrying over nothing?

If I fit this seal will my Bukh DV20 supply enough coolant flow to feed the shaft seal it's 4 L/min and still keep the exhaust as cool and muffled as it is currently?

I know it's possible to just fit a vent to a high point, but it's specifically not supported by Tides marine and I imagine would void the insurance for any claim in this area as well as the warranty.
 
I have a Tides seal. The pressurised feed is run as a T just after the raw water pump. There wasn't much room so I had to make a loop

setup.jpg


To regulate the flow I have a jubilee clip on the hose tightened up to restrict it to the required amount. I have had no problems with overheating by taking this T off.

Finished job
shaftseal.jpg
 
Maej,

I have the same model of Tides Marine shaft seal installed (MoodySabre) but mine is just vented to atmosphere. It's been in for two seasons with no problems. At the time mine was fitted I was told that Tides Marine recommended force feed water was only needed for faster vessels. They do seem to have changed that recommendation recently. Why, I do not know.
 
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This is my second Tides seal. I wrecked the first one by accidently running it dry (my exhaust exits under water so the noise is not so noticeable). Anyway, as well as shredding the impeller I noticed sometime later that there was water dripping from under the seal. When I took it apart the black bit under the forward jubilee clips had sheered right through. Just one clip holding the whole thing together.:eek: I spoke to Tides and they said that the seal will overheat quite quickly without a water feed - perhaps experiences like mine have made them change their recommendation. They gave me a small discount on my second one.
 
MoodySabre,

I think yours overheated because it relied on the pressure fed water. When that failed there was no vent to allow water back up the stern tube.
 
theoldsalt said:
Maej,

I have the same model of Tides Marine shaft seal installed (MoodySabre) but mine is just vented to atmosphere. It's been in for two seasons with no problems. At the time mine was fitted I was told that Tides Marine recommended force feed water was only needed for faster vessels. They do seem to have changed that recommendation recently. Why, I do not know.
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If it wasn't for the need for forced cooling supply I would have bought one without question already, but now they demand it I don't want to risk voiding my insurance.

From the look of how much water comes out the exhaust at idle, I don't think there would be enough flow to provide 4l/min to the seal and still be able to cool and muffle the exhaust. Maybe there's something wrong with my pump, or maybe I'm just being paranoid, it is hard to gauge how much comes out the exhaust without catching it.

I certainly wouldn't be comfortable diverting any coolant way before it goes through the engine, but again I'm probably being paranoid.
 
You could save all that hassle (and loads of money to help pay for your water tank) by fitting a Volvo seal. Needs burping once a year when launched and greased once a year. Nothing wrong with the Tides seal, but overkill for the application.
 
maej said:
Tides marine insist their seal needs a minimum of 4 litres a minute flow rate of coolant water... That sounds like an awful lot of cooling water to take away from a rubber exhaust hose that relies on the flow of engine coolant to cool and muffle the exhaust gas.

Am I worrying over nothing?

If I fit this seal will my Bukh DV20 supply enough coolant flow to feed the shaft seal it's 4 L/min and still keep the exhaust as cool and muffled as it is currently?

I know it's possible to just fit a vent to a high point, but it's specifically not supported by Tides marine and I imagine would void the insurance for any claim in this area as well as the warranty.
Click to expand...
Are you sure that the manufacturer's recommendation is not for a high revving mobo? Usually with a sailboat auxilliary engine, only a small water flow is required.
 
Tranona said:
You could save all that hassle (and loads of money to help pay for your water tank) by fitting a Volvo seal. Needs burping once a year when launched and greased once a year. Nothing wrong with the Tides seal, but overkill for the application.
Click to expand...
If you're on a drying mooring, all these burping types are a pain. There is a similar type on Vyv's website that has a breather incorporated which looks like the ideal.
 
The Radice seal is now easily available in the UK. It can be used with a vent for slower craft rather than force fed. It has the advantages of a Volvo seal without the need to burp.
 
Tranoma:
Thanks for the suggestion, the Volvo seal was my first choice, but having a 1" shaft and 1 1/2" tube means none of them are even close to fitting :(

ghostlymoron:
I was surprised by it as well so I checked on their own website, in the fiting instructions it details the need for 4L/min flow and in the knowledgebase it says...
"Some owners are tempted to forgo the water injection system on vessels such as these displacement hulls rather than planning hulls. In most cases, the column-head of pressure moving up the shaft is sufficient to keep the lip seal interface cool and the bearing lubricated. However, depending upon the efficiency of the propeller and its proximity to the propeller shaft through-hull, the Tides shaft seals can be deprived of necessary water. For this reason, Tides always insists that the water injection system be used to prevent potential problems of any kind."
Click to expand...
Quote taken from here

I think the alternative with a breather is the Radice seal, looks like a bulkier Volvo seal with a vent tube. I was also interested in that but haven't heard anything from anyone who owns one and I because of my inexperience I like to buy based on reviews.

There's the PSS that can be vented and has good reviews, but that just turns this thread in to another lip/face debate so perhaps better not go there
 
Simondjuk said:
The PSS seal only requires a vent and doesn't need burping.
Click to expand...

The PSS is a possibility and I know of another Sadler 34 that uses one, but I can't help but be swayed by all the hype over them. Still, my current thinking is I would rather the face seal than start messing around with my engine coolant.

So we have Radice and PSS that can both be vented without forced cooling.

Can anyone tell me the distance between stern tube and the bit of a PSS that sits on the shaft? Potentially if it is longer than my old seal I won't need to replace the shaft as it will sit on an unworn bit which would be a nice saving :)

Where in the UK can the Radice seals be bought from?
 
It is worth bearing in mind that when sailing and the shaft free to rotate there will be no forced waterfeed to the shaft seal whereas with the vented system water is always present on "slow" moving craft.

Maybe my Tides Marine shaft seal works while vented is because I have a relatively large clearance between shaft and tube allowing for good water access.
 
theoldsalt said:
Maybe my Tides Marine shaft seal works while vented is because I have a relatively large clearance between shaft and tube allowing for good water access.
Click to expand...

I was wondering if their reasoning was based on a situation where the prop is so close to the exit of the tube that when under power the prop would create a low pressure behind the tube sucking the water out, and in this situation the vent would simply let air in to replace it effectively doing the opposite of what it is meant to and drying the seal. There is also the situations where a bearing is inside the stern tube which would reduce the free water flow up the tube.

If this is the case it's a pain they don't just say that as my tube is free of obstructions and a good distance from the prop with a P bracket between.
 
maej said:
Tranoma:
Thanks for the suggestion, the Volvo seal was my first choice, but having a 1" shaft and 1 1/2" tube means none of them are even close to fitting :(


I think the alternative with a breather is the Radice seal, looks like a bulkier Volvo seal with a vent tube. I was also interested in that but haven't heard anything from anyone who owns one and I because of my inexperience I like to buy based on reviews.
Click to expand...

Couple of suugestions. To fit a Volvo seal you can sleeve your existing tube out to 1 3/4" to take a standard 1" shaft size seal. Think Radice seals are only available in metric shaft sizes so would not be suitable. Pretty sure that Volvo seals are made by Radice anyway - the difference in design (which is arguably an improvement for ease of greasing and reduced burping) is to allow them to sells seals under their own name.

BTW I have used a Volvo seal for over 10 years and the burping and greasing is really not a problem unless you are on a drying mooring. It soon lets you know if you forget burping as the dry rubber bearing part makes a horrible noise!
 
I asked the question of Tides Marine about the need for positive water feed, and all credit to their service I got a proper reply from Brian Raine at Tides Marine within 1 1/2 hours to explain, which is absolutely exceptional for responding to email queries in my experience.

He has said (paraphraseing) that although they ask for 4L/min, the seal only allows about 2L/min, they ask for 4 to make sure it is under pressure.

He also said that vented installations can let marine debris build up inside the seal which causes alignment issues with the bearing and lip which is why they insist on the pressure feed to prevent this.

Now I know why they want it, I'm still not happy about hacking into the coolant though.
 
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