Volvo shaft seal running dry

[Gazza]

We had a Volvo shaft seal fitted on our Eclipse over last winter, and, in common with others that we've had, it has worked well. However, over the past couple of months it has developed a habit of running dry, usually after we've been under sail for a while. There is a definite squealing noise, and the seal itself has been running hot; venting it then cures the problem.

I've been venting the seal before leaving our berth and this seems to have helped, but it still happens periodically - before anyone asks the question, the boat isn't on a drying mooring!

The engineer who fitted the seal, who I've relied on for the past few years, has suggested tapping into the seal and fitting a breather tube, finishing above the waterline. I know that this idea works on a number of shaft seals, but I'm wondering of anyone has:

1. Any experience of a similar problem with the seal running dry
and
2. Any thoughts/experience of putting a venting tube on a Volvo seal.

Any thoughts/experiences gratefully received.

 

[Kwik Decision]

We never had any problems like that with the volvo seal on our old Sadler 29. Thinking about it, if you heel over a lot, such that the prop shaft comes out of the water, that would cause the water to run out of the volvo seal. Otherwise there may be some turbulence whilst you are sailing, causing air bubbles to be dragged under the boat, which then float up into the seal, displacing water.

With regard to fitting a vent tube, while this will work in theory, I think I'd prefer to swap to a stern gland which comes from the manufacturer with a vent.

 

[Malish]

Yup, with this problem I would swap to a Radice seal which has a vent..

 

[ithet]

My Beneteau was fitted from new with a seperate input water supply from a seacock to the shaft tube just behind the Volvo seal. However the boat has a skeg so thereis dead space behind the seal which is probably why it needed a water supply.
In you case, if the seal has worked Ok for many years then I would suspect wear on the seal faces is leaking air so maybe time for a replacement Volvo seal.

 

[Champagne Murphy]

This might be a silly question, but are you greasing the seal regularly?

 

[Tranona]

First thing to do as suggested is to grease it and burp it. If the problem persists replace with a Radice which has a vent and greasing point.

 

[vyv_cox]

It does seem that some configurations of prop, shaft, rudder etc. have the ability to introduce air up the stern tube. Several owners have asked me questions about this but I have no answers.