Orbitrade shaft seal running hot

[Cantata]

I'm asking this question for a pal of mine, our chats over this haven't prompted him to ask on here yet.

Last winter he modified his stern tube and fitted an Orbitrade shaft seal, the variety that looks similar to the Volvo type but which has a vent, which we understand is to remove the need to 'burp' the seal after drying out. His boat lives in a mud berth so the shaft is likely to dry out each tide.

After sorting out some intial alignment problems, the transmission all works smoothly now but the seal gets pretty hot. The water in the vent tube he reckons is almost too hot to touch. He did grease the seal on assembly, in fact wondered at the time if he'd put too much in. He has tried burping it, which did seem to make it run slightly cooler, but he still regards it as hot.

I have to say that I ran 2 boats with Volvo seals, but I really don't know what temperature they ran at because it never occurred to me to feel them after a run. I certainly burped them before each trip, as I too was in a mud berth. Whatever, they were obviously OK as they lasted for years.

Any ideas please.

 

[Malish]

Sounds odd, he hasn't put a metric seal on an imperial shaft has he? (25 mm on a 1" shaft was a common cause of extra warmth as I recall)

 

[jwilson]

Is a vent tube actually fitted to the Orbitrade? Mine has a brass fitting for a vent but no vent fitted so I do have to burp after drying out, not a ptroblem with a boat on a deep water mooring as only once a year

 

[ditchcrawler]

On my Orbitrade seal the vent tube was quite high as the water level was well above the level of the shaft seal which is too be expected.
My understanding speaking to ASAP who I bought it from was that there should be water in the vent tube as otherwise that means there is no water in the seal. In the Volvo one which I had on 2 other boats you vent it as Dick says by burping and water comes out, but when you release it the water is sealed in and does the lubrication and cooling along with the annual grease for the lip seals.

 

[dankilb]

Has he considered connecting the vent tube to the raw water cooling circuit? I know that this is technically only required for higher speeds/mobos, but I have plumbed the vent this way on ours (Beta 50).

It just made sense (to me at least!) to do it this way - it still 'vents' via the same route as the anti-siphon (we've got a single breather 'manifold' that collects the anti-siphon and various tank breathers, going overboard high on the topsides), plus it means there is some circulation of water the other way (from the engine). This may help his cooling issue and maybe even to flush out any mud that has collected inside the seal. May it be that it is venting, but still clogged with mud, perhaps?

We've got a Michigan marine 'Volvo copy' that comes with a vent tube hose barb and greasing nipple as standard. We haven't used it yet, however, as the boat is still laid up.

 

[Pye_End]

My Radice seal runs fairly hot - hotter than expected. Doesn't seem to be a problem.

 

[Beneteau381]

I'm asking this question for a pal of mine, our chats over this haven't prompted him to ask on here yet.

Last winter he modified his stern tube and fitted an Orbitrade shaft seal, the variety that looks similar to the Volvo type but which has a vent, which we understand is to remove the need to 'burp' the seal after drying out. His boat lives in a mud berth so the shaft is likely to dry out each tide.

After sorting out some intial alignment problems, the transmission all works smoothly now but the seal gets pretty hot. The water in the vent tube he reckons is almost too hot to touch. He did grease the seal on assembly, in fact wondered at the time if he'd put too much in. He has tried burping it, which did seem to make it run slightly cooler, but he still regards it as hot.

I have to say that I ran 2 boats with Volvo seals, but I really don't know what temperature they ran at because it never occurred to me to feel them after a run. I certainly burped them before each trip, as I too was in a mud berth. Whatever, they were obviously OK as they lasted for years.

Any ideas please.

My VP and Orbitrade for a short while, 3 years, run cool. Two days motoring across Biscay and they get warm and make a strange sound, burping cured it, and it cooled off. The space between the prop and the cutlass bearing is important, 15mm minimum I found out. Otherwise the water from outside doesnt flow well up the prop shaft tube to it.

 

[Plum]

I'm asking this question for a pal of mine, our chats over this haven't prompted him to ask on here yet.

Last winter he modified his stern tube and fitted an Orbitrade shaft seal, the variety that looks similar to the Volvo type but which has a vent, which we understand is to remove the need to 'burp' the seal after drying out. His boat lives in a mud berth so the shaft is likely to dry out each tide.

After sorting out some intial alignment problems, the transmission all works smoothly now but the seal gets pretty hot. The water in the vent tube he reckons is almost too hot to touch. He did grease the seal on assembly, in fact wondered at the time if he'd put too much in. He has tried burping it, which did seem to make it run slightly cooler, but he still regards it as hot.

I have to say that I ran 2 boats with Volvo seals, but I really don't know what temperature they ran at because it never occurred to me to feel them after a run. I certainly burped them before each trip, as I too was in a mud berth. Whatever, they were obviously OK as they lasted for years.

Any ideas please.

I have no idea how hot my VP seal gets as i never touch it! May be the mud-berth has something to do with it. If any mud gets forced up the grooves in the cutless bearing it may delay the water flowing and equalizing in level in the vent tube. After refloating, blow down the vent tube to clear any mud and watch to see the water level return (assume you have a clear tube), then go for a spin to see if it is cooler. On motorboats where running times are longer it is normal for these type of bearings to be fed with a water flow from the raw water circuit or from a scoop skin fitting.

www.solocoastalsailing.co.uk

 

[Cantata]

Thanks for the suggestions. I'll pass them on and take it from there.

 

[Neil_Y]

Thanks for the suggestions. I'll pass them on and take it from there.

Just a thought, but has it got a forward bearing and has it got a greaser? many people over grease the stern tube and grease is a poor conductor of heat so you can cook things with too much grease. Water is the best lubricant and coolant.