Couple of things for you to think about
I looked at a lot of engines to repower it, think I'd finally settled on Yanmar 240 but not close coupled and bravo2 and a reasonablly cheap combination. I fell in love with GM's V8 diesels in principle, but there are a few horror stories floating around www.marinediesel.nu
and also peninsular engines in the US.
I have been told that someone had a 250Hp six cylinder sabre driving a P22 through a 101 leg and didn't have any problems, don't think I'd like to try this - too much torque!
I went to look at a P22 in Cowes that had had the engine box moved right aft and a close coupled Volvo KAD 32 fitted, according to what I heard from people down there the deck at the stern was awash at rest, and water continually found it's way in - was kept afloat by a bilge pump! I suspect that you have to have a mid mounted engine in a P22.
Another engine that may be worth a look is the Steyr marketed by Mermaid, I think it's about 260Hp frommemory but very light, apparentlt it's been fitted to quite a few superyacht tender ribs.
Have to say that I bought a Sternpowr leg and Mermaid turbo 4 to get it going with a view to repowering it later.