Stern Tube Leak

woodster · Nov 9, 2013

have you check your stuffing box on the other end of that shaft...it could be coming from there ...also i noticed that your prop and zinc don't seem to have much clearance between them

regards

woody

Ralph Johnstone · Nov 9, 2013

Couldn't help but notice the surface on the stern tube. Is that threaded ? ? ? ? or just random grooving on the surface.

If threaded, and finding a nut that fits, you may be able to remove the zinc and prop and then apply a soft rubber gasket and sealant. Sealing surfaces would have to be spotless for this to seal.

If not, back to the drawing board.

BobM · Nov 14, 2013

zinc/prop clearance

I agree. If you have inadequate clearance that may be the cause for the repeated cracking/failure. I'd try a smaller zinc. The other thing is that you may need to make a wider fillet of caulk between the tube and the keel.

woodster · Nov 17, 2013

klemsaba said:
Went out to do some more winterzing on the boat today. I have enough clearing with the zinc but the entire stern tube is loose and I can rotate it. I guess the prop shaft will need to come out.

you may be able to remove the stern tube from th rear...if you can clean it up and try not to damage it theses things cost about 40 dollars a foot and are sold in a minium footage cant remember how many feet i think it 4 ft ....that is some kind of hi tech fiberglass weave thay use to make it ....try pulling the prop and the zinc and see if you can get it out ..if you can clean everything up and reinstall it wit west system 6-10 or maybe G-flex......good luck...

regards

woody

fa102 · Nov 19, 2013

The stern is frp. (looks to be the same as on my 1978 S@ 8.
The leak probably due to cracks where the tube meets the keel's trailing edge;
possibly caused by strain on the tube from engine-prop shaft missalignment / excessive engine vibration / etc. etc..
Repair would entail: removing the prop shaft after opening up the shaft stuffing box. (may need to drop the rudder to get the prop shaft out.
removing the stuffing box assembly and the hose that attaches it to the
stern tube.
look for cracks @ / around the tube; properly repair the frp. crack (retain services of a qualified frp. repair tech if you don't have the
check the prop shaft for straightness and wear @ cutlass bearing area.
clean & balance the prop.
install new cutlass bearing (in the stern tube.)
inspect the engine mounts (their cushion material wears / collapses over time); install new mounts as needed.
clean and repack the stuffing box (I like the synthetic packing); get new hose & hose clamps; or install a new dripless type unit.
install a "donut" type shaft zinc (they are shorter than the zinc you use and give some clearance for water flow to the cutlass bearing.
re-assemble all.
*** check & adjust engine alignment (vessel on land & afloat) for correct alignment before running underway.

I have done all of the above work (no shaft tube repair needed) on my
S2 8.0C.

Frank A (Long Island NY)

fa102 · Nov 20, 2013

klemsaba said:
Hi Frank. Thanks for the detailed post. If our setups are the same you know how little room there is in the bilge where the prop shaft enters the boat! What a pain!

One question... what are you referring to 'frp'?

Your welcome. (all based on my experience and self done work).

frp. abbreviation for fiber-reinforced -plastic / fiberglass; grp. (glass reinforced plastic) is another term used.

Set-up in our boats should be the same. A lift off carpeted 3-sided plywood box (on the sole
in the aft cabin covers the shat stuffing box (in my 1978 8.0C).
The tube's surface pattern (in your photo) looks to be the weave of the cloth laminate.

I disassembled all (including the rudder & steering gear) 5 years ago to install a new cutlass
bearing. Removing the cutlass bearing (typically they don't just slide out after removing the set screws) was a slow delicate process (to avoid damaging the frp. tube); used a hand held fine tooth hack saw blade to make a lengthwise cut through the old bearing (allowed it to be
then pinched & pulled out (a three hour job).
If you don't have a lot of experience with mechanical work you need to find an experienced marine mechanic who has done similar work.

romanijoe · Mar 19, 2014

When I dropped the rudder in my 79 8.0C I had the same issue of figuring out how to release the rudder. I disconnected the stainless steering cables and the then unbolted the four bolts that securing the steering quadrant. I had a friend on the ground supporting the rudder since I wasn't sure when it would fall loose. Once I removed the four bolts the rudder slipped free along with the square SS stock that locks the quadrant to the rudder post. The rudder weights probably close to 50 lbs so be ready.

fa102 · Mar 20, 2014

The responses (need to unbolt that bronze quadrant) are correct. Additionally you should loosen the rudder shaft stuffing box all the way. Suggest support the rudder with a scissors jack to lower it down (rudder assembly is quite heavy); hope the boat is blocked high enough.

Recommend remove the bronze stuffing box assembly (the original lag bolts on my boat were rust wasted away. Check the wood core of the molded frp. construction that the shaft log mounts on. Use bronze lag bolts when reinstalling the shaft log; which needs to be set on bedding compound for water tightness. If the original lag screw holes are worn; just rotate the stuffing box flange 90degrees and drill new holes.
Pre-cut new rings of packing (use the rudder shaft as a form to cut the rings to the proper length.) Check / adjust the packing after the boat is afloat and working the steering.

Use marine grade anti seize when reassembling the nuts & bolts.

I see that the steering cable turnbuckles are tightened all the way; it is possible that the cable has stretched.

Bevel (with a fine file) the rudder shaft edge prior to reassembly.

Were there set screws in the frp. stern tube to hold the cutlass bearing in place?
If no you should install 2 small dia. set screws at least 45 degrees apart: Use ss. fine thread set screws with loc-tight; get the correct size drill & tap to create threaded holes in the frp. tube.

Most Important: Make sure that all of the engine mounts are in good condition; if not replace them (if not the new cutlass bearing won't last long). Check engine -shaft coupler
alignment & adjust before launching the boat. Check / adjust again after afloat for a day or two after briefly running the engine in gear.

Good luck.

FA

fa102 · Mar 21, 2014

klemsaba said:
Thanks for the tips! Good observation about the turnbuckles. The cables are actually a little loose. I'll have to look into that.

I have the set screws still. The threads also look good in the stern tube.

Remember to use a donought type (shorter than the torpedo type you were using) shaft zinc as it provides some clearance to allow sea water
to enter & lubricate the cutlass bearing.