Attempting to put an outboard on a boat that size is an unworkable idea. IF you are able to hang one off the stern, you won't be able to reach it to operate it. IF you can reach it, it will provide lousy service. The P31 is a nice boat, unless you want to reduce its value to zero, you need to install a working inboard. In terms of new engine, a Yanmar is the way to go.
Hopefully, you figured the new engine cost of $10-12,000 grand into the price you paid.
Certified...in several regards...