Radice shaft seal a word of caution

[mickbond]

Last year I replaced my Volvo Shaft
with a Radice seal. The new seal has a vent pipe that removes the need to burp the seal. This pipe is taken above the water line ( in case 20" above) and vents off any air. The seal has been a complete success or so I thought. Yesterday when in a Dutch lock I had reason to go from slow ahead to full astern rather quickly
All was well but on checking the bilge later there was a quantity of clean sea water in the normally dry bilge. I couldn't find the reason at all. After much investigation I found some salty deposits on the end of the vent pipe. What had happened was that with the boat moving forward, when full reverse was applied the force of water from the propeller had pushed water up through the vent pipe and into the bilge. I fastened the boat tightly to the pontoon selected full reverse and hey presto water came flooding out of the vent pipe. As this is something I never do I've never noticed it. On full reverse when not fastened to the pontoon the water stops being forced up the pipe as soon ad the boat starts making way and do only a small amount enters. I have plugged the pipe with a wine bottle cork to prevent this happening again, as once the boat is in the water it shouldn't need burping until it is hauled out. Permanent solutions are to feed the seal with water from the cooling system as recommended for high speed craft ( of which mine definitely isn't) or try raising the level of the vent pipe to see if the head of water the prop can generate is less than the height I can make the vent.

Any comments?

 

[nedmin]

I hope your Radice seal lasts as long as my Volvo. Now 12 years and not a drop of water and this in the silty waters of the Humber,Trent Ouse etc.

 

[prv]

I reckon go for a long and tortuous route to the hose. As I understand it, it's just there to let the bubble of air at the top of the stern tube escape when the water rises up the tube after drying out. A long and winding hose shouldn't prevent the air doing that, but hopefully will slow down the surge of water.

Pete

 

[RAI]

A longer hose could exit the hull well above the water line, or into a cockpit drain.

 

[Modulation]

I reckon go for a long and tortuous route to the hose. As I understand it, it's just there to let the bubble of air at the top of the stern tube escape when the water rises up the tube after drying out. A long and winding hose shouldn't prevent the air doing that, but hopefully will slow down the surge of water.

Pete

I agree with that. I've just replaced my 20+ year old Volvo with similar after the original did sterling service. Mine never needed burping as the boat builders (Beneteau} provided a vent pipe from the top of the prop shaft tube - just behind where the shaft seal is fitted. That pipe follows a fairly tortuous route but finally ends about 1.2 m above the prop shaft. Never any problems motoring fast in reverse

 

[mickbond]

Thanks for that I will extend the pipe tomorrow and see what happens. I reckon I can raise the end by about 1 metre

 

[Alpha22]

Expansion bottle???? Vented of course.

 

[PetiteFleur]

Interesting - I've fitted one to mine and a second to a friends boat, so will check if it happens. Both vents we positioned as high as possible so perhaps it won't be a problem.

 

[Alpha22]

I guess a lot will depend on the shaft log, cutless, underwater boat profile and prop shaft angle ...... and probably more.

 

[mickbond]

Have just added another metre of pipe and now the pressure is not enough to reach the top on full reverse. A height of 2 meters above the prop shaft.

 

[ghostlymoron]

2m is quite a head. How about fitting an isolator in s convenient place? You only need to open it after drying out but you could also do it when at anchor just to check. I like the look of the radice seal, it seems to take over where the Volvo left off.

 

[macd]

I hope your Radice seal lasts as long as my Volvo. Now 12 years and not a drop of water and this in the silty waters of the Humber,Trent Ouse etc.

Not aimed at your post directly, except that it highlights my quandary...but as I've posted before, the bumf accompanying the Radice seal recommends replacement after a mere 400 hours. This may or may not be ultra-cautious; it may or may not be a device to increase sales. But I'd be very interested in the comparable figure for a Volvo seal, assuming there is one.

 

[jakeroyd]

Replaced my Volvo seal after 15 years and admittedly low hours.
No leaks at all.
IIRC the Volvo reccomendation is 7 years.

 

[Tranona]

Not aimed at your post directly, except that it highlights my quandary...but as I've posted before, the bumf accompanying the Radice seal recommends replacement after a mere 400 hours. This may or may not be ultra-cautious; it may or may not be a device to increase sales. But I'd be very interested in the comparable figure for a Volvo seal, assuming there is one.

Volvo recommendation is in years rather than hours - and massively conservative. Given that it is also made by Radice don't suppose there will be any difference with their own branded version.

 

[macd]

Volvo recommendation is in years rather than hours - and massively conservative. Given that it is also made by Radice don't suppose there will be any difference with their own branded version.

Thanks, Tranona. That helps. (And will save me a few bob since I've recently fitted one.)

 

[thalassa]

I've got a Radice type seal, going under the Dutch name Exalto, for six years now. The vent hose is about a meter and extends above the waterline. A small valve closes the hose off. When starting, I open and close the valve for a few seconds to allow water in the shaft (drying marina). Not a drip out of the seal yet.

 

[Danbury]

I have the same seal fitted.... but on mine the hose is connected to a water supply off the engine... so it gets water fed into it, not air escaping from it... is this wrong ??

 

[vyv_cox]

I have the same seal fitted.... but on mine the hose is connected to a water supply off the engine... so it gets water fed into it, not air escaping from it... is this wrong ??

Nothing wrong with it, normally fitted to boats capable of higher speeds, which can draw water out of the stern tube.