Shortest shaft seal

[snowbird30ds]

I would like to convert from stuffing boxes to dripless shaft seals but don't have much space between coupling and hull, what is the shortest dripless seal?
I have 1 1/2" shafts.
Current sterntube and stuffing box is a one piece item.
Thanks for any useful info.

 

[RivalRedwing]

Volvo / Radice probably, they are shorter that PSS anyway.
See here too for some visual comparisons: Stern glands

 

[Keith-i]

Lasdrop are pretty short too.

 

[Tranona]

Volvo type seals only go up to 1 1/4" in Imperial. best alternative in my view is Tides Marine Sureseal, also lip seals by serviceable 7 1/4" minimum gap from face of stern tube to coupling tidesmarine.com/wp-content/uploads/2021/10/sureseal_catalog.pdf
Available from Sillette/ Lake Engineering.

 

[snowbird30ds]

I only have 180mm from hull to coupling so may be destined to stay with existing glands by the look of it, it seems the orbitrade seal is 120mm long.
Port engine has always been worse than starboard so may need to take a closer look at engine mounts as both have been alignment checked but has to be done out of the water.

 

[Tranona]

I wasn't aware that Orbitrade made a 1 1/2". That will work fine in a 180mm space assuming you have the 58mm diameter stern tube to attach it to.. You will have to move the shafts back to install it (or the engines forward!) but I have fitted this type with far less clearance - about 150mm for the smaller 110mm long version.

 

[snowbird30ds]

My 180mm is from flat hull face where existing gland is fixed, unless the short bearing carrier on the outside has a stub I may well be knackered, I was originally hoping I could modify the existing gland to a stub but not holding up much hope now.
Will have to take apart to see how it is constructed.

 

[Tranona]

If you have the common bronze stub housing on the end of the stern tube you should be able to remove it and have machined to take the Orbitrade. That is what I did on mine. I also had a length of cutless inserted to provide an interim bearing as the shaft is very long. Photos show the machined housing and the final installation. Machining done by Lake Engineering.

 

[snowbird30ds]

Mine isn't a stub, it's a stuffing box.

And being a 1.5" shaft and 10mm packing it's going to be pretty much 58mm ID so nowt left to machine, if the seal had been shorter I would have made an insert from thick walled bronze tube with an o ring groove and used grub screws to retain, but from gland face to coupling is only 118mm.

 

[rogerthebodger]

That looks similar to how my stuffing box looked like bolted to a flange on the inner end or the prop tube.

I made a stub with a flange to replace the stuffing box so the tube of a dripless seal can fit onto. In my case I used a PSS seal

My prop shaft is 40mm dia so similar to yours

 

[Tranona]

Mine isn't a stub, it's a stuffing box.
View attachment 182912
And being a 1.5" shaft and 10mm packing it's going to be pretty much 58mm ID so nowt left to machine, if the seal had been shorter I would have made an insert from thick walled bronze tube with an o ring groove and used grub screws to retain, but from gland face to coupling is only 118mm.

Similar to mine before I removed the stuffing box. I had to get it machined down to 48mm with just enough wall thickness to take the 40mm OD cutless.

Suggest you take it apart and check how much clearance there is between the shaft and the tube and whether there is enough meat in the flange to screw in a 58mm OD 5 or 6mm wall thickness bronze tube which will give plenty of clearance for the shaft. You can also get rid of the greaser feeds with plugs like mine. No need for that wire to the anode either.

 

[snowbird30ds]

My hull does not have a tube as such, it is a wall of grp as it is a mobo and shaft goes into a tunnel underneath, not sure about losing water feed as it's a 20 knot boat and don't want to overcook the seal.

 

[rogerthebodger]

Where the existing stuffing box is bolted onto the GRP wall fit a tube with a flange welded to it to pick up the bolts that currently hole the stuffing box. The tube only needs to be 20/25 mm long so the the new dripless seal can slice over the tube and clamp onto the tube as a watertight seal

some seals like my PSS do have water injection connections for higher speed boats

This PBO article may help you to select which one will fit your setup

Dripless Shaft Seals - Buyer's Gude - Practical Boat Owner

 

[geem]

The shortest is a deep sea seal but they don't suit every installation. If you have longitudinal play they don't work well at all. I would love to change to a different system but nothing else fits in the space of a deep sea seal

 

[Tranona]

My hull does not have a tube as such, it is a wall of grp as it is a mobo and shaft goes into a tunnel underneath, not sure about losing water feed as it's a 20 knot boat and don't want to overcook the seal.
View attachment 182940

The Orbitrade has its own water feed/vent. Used as a water feed for boats like yours or a vent above the waterline for sloboats like mine. Although you don't have a tube downstream of the stuffing box you still need to consider clearance in the stub that the seal is attached to. Pretty sure when you unbolt that from the hull and remove the stuffing box you will be able to modify the stub to take the Orbitrade. Plug the water and grease feed on the housing and attach your water feed to the spigot asap-supplies.com/products/orbitrade-91876-1-stuffing-box-seal-kit-for-1-1-2-prop-shafts-orb-91876-1 The little plug is for greasing once a year.

That would make a very neat installation

 

[snowbird30ds]

Thanks all, I will have to see what is on the outside of the hull once I get it out of the water and see what I can do, I'm pretty sure there is a bronze housing with half bearing on the outside and bearing could do with changing anyway.