Replacement of Stern Tubes
by Steve Leonard, December 2014
Pertinent to some Deltacraft owners is the need to replace the stern tube, seldom before the boat is 30 or so years old!.
If so then the job I'm undertaking at the moment may be of some assistance, because I can show in steps the necessary procedures on the above Mark 1.
A marina in Sydney's middle harbor last week quoted $5,000 to do the job which is quite outrageous really but business is business I guess, however my sympathy lies with the owners so please pay attention!
First of all is it necessary to replace a leaky stern tube? (the tube which carries the shaft via the stern bearing and the gland at the front).
No, actually its best to sleeve it, which is what I will do in order to stop it leaking, which in this case is due to electrolysis. NOTE:- always object to welding on boats near to your boat for this reason, it can initiate electrolysis, metal breaking down.
1. The only place a GRP boat can leak from is from a hull penetration, since I have yet to see a hull holed in an Islander, its either skin fittings, self drains, or stern tube. So remove the boat from the H20.
2. Separate the couplings and take the shaft out and remove firstly the rudder which needs to be dropped to accomplish this. Just take off the tiller arm and the rudder is free.
3. If the coupling fails to come off the shaft then, after much effort to remove it... give up, and cut it off with an angle grinder (100mm) all care taken, this is dangerous. Then of course have to have a new one machined.
4. After the shaft is out remove the gland which is hose clipped onto the forward end of the stern tube.
5. Remove the stern bearing by twisting it with multygrips. This will be discarded and a new bearing machined to fit the tube. You may need to grind the GRP holding the bearing and replace the glassing later on.
6. Measure carefully the internal diameter of the tube and procure a sleeve, either in stainless steel or my preference plastic or GRP (which is completely inert) that is a neat not loose nor tight fit.
7. Reem out the stern tube so as to get a key for the epoxy glue which will hold in the sleeve.(emery paper on a dowel will do.)
8. Slide in the tube into an epoxy bed.
9. Allow to cure and fit the new stern bearing, glass it on the outside of the keel.
10. Refit the gland, shaft, coupling, and realine the engine if necessary.
11. Its important to check to see that the shaft is central in the new tube sleeve.
12. Make sure there is a clear gap between the tube internal diameter and the shaft.
13. Have a beer !