[hiccup]

have had the same challenge. It's hard to get any leverage on the rotor when you're bent over leaning in the bilge. On my 38 I can get 2 spreader clamps in there (something like the DeWalt DWHT83148) and they make it easy.

In my last boat, which was a 33, it was a little tighter and I had to build a contraption to move the rotor. I used a bolt with a washer and a nut. I threaded the nut on nearly all the way, then the washer, then stuck it in a hypo tube. I cut the hypo tube so that the contraption was just a little shorter than the distance between the rotor and coupling. I made two of these contraptions and spaced them 180 degrees apart on the shaft in between the rotor and coupling. I used masking tape to tape them in place. Then I used two open-ended wrenches to move the nut away from the bolt head a few turns until it started pushing on the rotor, did the same to the other contraption, back and forth. This made it extremely easy to precisely move the rotor the exact amount I wanted to. I had the stuff laying around. If you don't have hypo tubes you can use a piece of pipe or even a wooden dowel with a hole drilled in it.

Measure the distance between the rotor and coupling before you start and write it down along with your target distance. Make a mark on the shaft with a sharpie. Lightly tapping it with a phenolic hammer might work but I absolutely would not start swinging a steel hammer with any force at it.