NEWPORT-33

Prop Shaft Coupling Upgrade:

I found that the stubby little shaft coupling that came on the boat to be totally inadequate. In fact, the coupling became loose, and finally sheared off the key that is in the shaft. What makes the coupling inadequate is that it is too short (meaning the coupling captures too little of the shaft), it's not a split coupling (meaning it cannot "compress" tight over the shaft), and it has the locking press bolts in opposing locations. If your shaft coupling is short, meaning 2 or 3 inches long, and has two opposing bolts (180 degree opposing) into the shaft, then you might consider replacing it.

The best fix, IMHO is to get a 3 1/2" or 4" long 7/8ths. ID split coupling. It should have a key way in it, with at least 3/8" bolts that are 120 degrees and 240 degrees from the key way. This works best as you first slide in the shaft. Then tighten the split in the coupling (two flange bolts), and finally, wrench in the two bolts that are in the coupling that screw into detents in the shaft itself. With the 120 and 240 degree orientation, these bolts when tightened, press the shaft towards the key way. It's important that you pre assemble the coupling on the shaft, then have a machinist chuck this entire prop shaft assembly into a lathe (remove prop first) and have them turn or "face" the coupling to make sure you have a perpendicular surface to bolt to the back of the transmission. If you don't do this final step, you may never have a true surface for properly aligning your engine to your prop shaft.

Follow the instructions for aligning your motor, and remember to align it in the water, and not in the yard on stands which support the boat differently than the sea. Nothing holds her more dearly than the sea...

I needed to move the engine (Universal Diesel Twin - approx. 14 hp.) forward in the engine forward to allow me room for this longer coupling between the stuffing box and the coupling on the engine. What I did was buy new engine mounts (three total) and bolt them to the engine. I then placed the prop shaft (and assembled coupling) in the boat. By locating the prop shaft fore and aft, leaving enough room behind the coupling to access the packing box, I then moved the motor around to where I had the engine aligned with the prop shaft. Now I marked the location of where to drill the new engine mount holes, removed everything, and then bolted everything in place, with the final alignment using 0.002" feeler gauges.

This is a similar procedure for any inboard powered sailboat with shaft drive. But the fact the there may not be as much room between the stuffing box and the engine might require engine relocation forward. Hope this helps. Feel free to contact me with questions.

N. Mark Wiltz
http://w3.gorge.net/casiera
sail@gorge.net