Join Date: Sep 2005
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I did this same project with my Tartan 34 over Christmas.
I recommend cutting the coupling. I used a 4" angle grinder and a Bosch oscillating tool to cut through the coupling on top of the keyway and then 180 degrees on the other side. It was messy, but way better than messing with heat and cold approaches for the reasons you noted. I also didn't put a scratch on the shaft. Had it not been for the scoring I found at the stuffing box, I would have easily been able to reuse the shaft. The whole thing took 45 min, tops.
Next, check the clearance between the dripless/stuffing box of your choice and the coupling. If you have an inch to spare, your next coupling could be a split coupling. The advantage is you don't press the shaft onto the coupling. Instead, the coupling has a slot that closes when you bolt it down. The downside is the coupling is about an inch longer.
Should you not have the space for a split coupling, make sure you have a small sledge to seat the shaft onto the coupling. I ended up using a scrap piece of 3" drive shaft to wail it into place. Every time you hit the shaft, the engine moves forward on the mounts and it takes forever. Not a fun project, but it's the only option unless you hoist the engine and slide the pressed coupling/shaft combo back through the packing and stern tube.
While you're in the neighborhood, have a look at your cutlass bearing and strut. A bearing is only $20 and the easiest time to replace it is when the shaft is out. If your strut needs rebedding, as mine did, it's a good time to get it taken care of. On many boats, mine included, the rudder is in the way of removing the shaft and dropping the strut was the only way to get the shaft out, short of hoisting the engine or dropping the rudder.
Finally, if you haven't had enough good advice from your friends yet, consider having a prop shop balance your prop. Mine had significant differences in pitch and diameter. Friends who've had it done say it made a huge difference in vibration and the cost for a 2 blade is only $200-ish.