Sagar Marine Hull & SternTube

[spannerman]

My boat is currently in dry dock for a variety of work including a leaking stern gland - a straight forward job it would seem but no such luck.

 

Apparently a "standard fitting" consists of a threaded boss welded into the hull into which a stern tube bearing is screwed. On the other end of the stern tube bearing is screwed a "packing box??" containing the packing rings

 

On my boat the stern tube bearing and the section containing the packing rings are all one cast/machined piece screwed into a boss of non standard diameter and totally different thread to anything in the local chandlers, just to rub salt into the wound, the prop shaft was 1 1/2" diameter turned down to around 1/1/4" to fit the stern tube but with the 1/1/2" taper left to fit a 1/1/2" prop - the boat yard fitter called this arrangement unique - at least I think that's what he said as he was head down in the engine hole muttering and cursing at the time since the modified shaft had been fitted right through the split coupling and the prop shaft had to be cut into two to remove it from the boat

 

The upshot of all this is in the short term, the prop shaft & the propeller will need to be replaced so I can leave the dry dock but I would like to source a suitable stern tube to replace when the original 24 year old one is worn out, so far without success

 

Has anyone got any knowledge of this type of stern tube gear please

 

 

 

 

[Timleech]

Sorry but I don't follow your description - it reads to me as though the shaft is 1 1/2" at either end and 1.25" in the middle, that would be impossible to assemble into the tube. Obviously I'm misunderstanding something.

 

Yes I have once or twice, years ago, seen your sort of stern tube, but they're probably no longer available.

Consider getting the existing tube bored out and sleeved, assuming it doesn't carry a 'slip in' bearing, when it's too worn for further service.

 

Tim

[spannerman]

Sorry, I didn't explain myself very well. The prop shaft was machined from 1/1/2" down to 1/1/4" for the full length other then the taper where the prop fits - hope this makes more sense

 

I'm glad someone has at least seen a stern tube fitting like mine - I suspect you are right, we have searched high and low for a replacement today but to no avail

 

Boring out and sleeving was an option but outside the available timescales this time so it will have to wait until next time the boat is out the water, at least I will have some time to plan for the work

 

thanks for your swift reply

[arbutus]

I had a new 45 foot Sagar boat built in 1981. From what I remember, it used an inch and a quarter prop shaft and a stern tube with a stuffing box on the end inside the boat and a cutlass bearing inside the external or canal end of the stern tube. The cutlass bearing is a polyurethane tube with grooves in it, which the prop shaft runs in and is water lubricated. There are two holes in the stern tube close to where it exits the hull, water flows through these holes and along the grooves inside the cutlass bearing to provide lubrication. I was warned not to over grease the stuffing box inside the boat as excess grease could leak along the stern tube and block the two holes that provide water lubrication. I’m pretty sure it was a Vetus prop shaft, stern tube and cutlass bearing. Vetus still sell them, look on their web site. The rest of the engine installation consisted of an Aquadrive coupling and a 1.5 BMC marinised by CT Marine.

[spannerman]

thanks arbutus but mine is not a vetus water lubed stern tube - pity as they seem easily available