J/30 Class Association Forums J/30 Forum The Boat, Sails and Equipment Shaft replacement

I know of one J/30 owner who increased his propeller shaft size from 3/4 to 7/8. Is this a common upgrade to reduce vibration and whirl? At the same time, did anyone replace the log/stuffing box assembly? Mine works well but is hard to inspect because the rubber hose and clamps are partly burried in glass. I'm concerned about rubber 20 years old!
Seth Hunter/Bayou Bleu-270/hunter@i-stat.com

I replaced the rubber tube last year. Had to chisel out the clamps on the log tube. Don't know why things were asembled that way. Didn't damage the log tube with the chiseling and it went back together easily. I had the shaft balanced at the same time. Runs nicely.

I did this upgrade and was pleased with the results. You will need to replace the cutlass bearing(the 7/8 bearing has the same OD as the 3/4), ream out the shaft log tube a bit to increase the clearance, and bore out the stuffing box to the larger diameter, and of course put in new packing of the correct size. None of this was particularly difficult. I opted to keep my existing propellor, so the shaft had to be machined to accept the 3/4 diameter taper. It probably would be better to go with a new prop hub with a 7/8 taper, but this did work OK for me.

Thanks for the feedback. Do you recall what material the log tube was made out of and how much wall thickness there was after opening it up?

The shaft log tube is made of fiberglass. I used a small diameter rasp and then a drum sander on my drill to hollow it out a bit. I used a spade bit extension shaft to make it long enough to get inside the tube. I don't recall the wall thickness, I think it might have been around 1/4", but it was enough to let me feel comfortable in removing a bit of material from the inside wall of the tube. I also passed a rag smeared with epoxy through the tube afterwards to seal the surface that I filed away.

I had a bit of trouble with the prop strut, it was out of alignment with the shaft log tube and I could not get the new shaft to line up and go into the opening. This was not apparent with the 3/4 diameter shaft (but may well have contributed to the vibration we were experiencing). With the help of my mechanic friend, we removed the cutlass bearing, and used an old thick prop shaft to lever the strut into proper alignment. This was tricky, but worked.

You can email me at roulton@smss.com if you want to discuss further directly.

I recently removed the stuffing box. The rubber hose for the stuffing box is glassed on the bottom and the hose clamps wouldn't come off. To get the clamps off I unscrewed them all the way loose then pulled them out along their length, then I pretty much tore up the rubber hose getting it out.

I replaced the old stuffing box with the PYI dripless seal. Works like a charm.

Thanks for the feedback. Got it out OK.
Incidentally, my log (and strut) appear to have been set in glass poured into large rectangular cut-out. Inner skin has detached from filled area - not surprising since effectively a butt joint. I'll reglue skin to core (check that it's dry) and glass-over joint to filled section, sealing it up. It's worth reinforcing that joint before it separates.

Correction - floor of engine compartment around log tube is not "inner skin" - air, not balsa, underneath (about 1" air gap to hull). Sorry for error.