I went to a 10 pitch and it was too much. An 11 for my 55hp was just right. I would guess the 10 will work much better than what you have now regarding your 45hp engine. I did some poking around here on iBoats, The top RPM range you should be getting to is about 5k rpm's, at above 20 closer to 25, depending on load and water conditions.
Now, regarding the trim, (and assuming no power trim!) there is a horizontal pin on the mount that the motor catches on, right?. That has different mounting holes. On mine I tried the closest one to the hull, and it planed well for a couple of seconds then it was obvious it was plowing, so that lasted about 10 minutes. I believe the second one out was what I settled on, the 3rd hole up tried to porpoise, and did not come out of the hole and plane as well. You need to experiment some. I tied a small heavy duty cord to the boat and that pin, did not want to drop it in the water.
Good luck!
p.s. my old '72 is still one of the favorites I have owned. With just the driver, I could get up on a slalom ski, took a while and had a specific technique. I weighed 250 at that time. Two skis was no problem, I even had two very trim skiers up at the same time with it, was a fun boat.
