ben2go
Guru
The Perkins 4.236 is certainly up to the job. I put over 4500 hours on one, which had a mid life rebuild (at about 4000 hours--didn't need a rebuild, but the PO didn't know how to change the main oil seal without taking the engine out of the boat!) The engine was completely examined and all was up to spec at 4000 hours. Since It was apart we put in new mains, and any part which seemed to wear. I sold that boat 20 years ago. The next owner still lives aboard and the engine still ticks over. That boat was a Cal 46, Displacement 30,000# lite boat, we sailed her fairly heavy, often with supplies aboard for 6 months. The specs are very similar to your boat (beam LWL and hull form just more draft with the keel)--she would run at a gallon an hour at 6 knots at 1600 RPM. Max speed was just shy of 9 knots. We never ran over 8 knots--and rarely did that. I consider that Perkins a great match for your hull.
Remember that "Idlewild" did her circumnavigation with a 55 hp Izusu. (She was 30,000 lite boat, 57' LOA, and 11' beam.)
Congratulations, she looks to be a well found and constructed vessel.
Idlewild Idlewild