i own a p22 that we had converted with a yamaha 275 hp 6 cylinder diesel. It runs a 1.32 : 1 sternpowr leg no problem, because we had increased the hp by so much we were able to keep the gear ratio and the prop the same. so we have gone from 27 knots at 2650 rpm to 36 ish knots at 3500 rpm.
to use a high revving engine of less than 240 hp will not work with the 1.32 : 1 leg. You will require a 1.66 : 1 and this is standard config for p22's that have the newer yanmars in. If your leg does say yanmar on the back, it is possible that it is in fact a 1.65 : 1 as most early ones were converted 1 32 :1 and were relabelled, or it may be that yours was a special.
out of interest we are putting in a yanmar 315 6 cylinder at the moment and I am hoping to use a 19 " prop on the same but deeper 113 leg.
I wonder if the boat will top 45 knots?