Diesel Conversion 23cc

[Harper]

Greetings,
I am nearing an agreement to acquire a potter series straight I/B 23cc. I currently own a 240hp yanmar with a bravo 3 duo-prop outdrive. The engine and bravo 3 have less than 100 hours on them. As I would have to remove /sell the bravo 3 and refit the engine with a new bell housing a configuration to straight I/B is possible.
Can I get opinions on the suitability of repowering a straight I/B (currently 350 260hp) with a yanmar 240hp? Will this unit provide reasonable performance or would I be setting myself for disappointment? My expectation is a cruise in the mid to low twenties and a WOT somewhere shy of 30kts.
Thanks in advance for the wisdom.