Size wise that boat would fly with a Marine engine in that size class. That airplane engine is a bit lower performance than a marine engine, it should have a decent amount of torque, it just won't turn up the rpm's as high or as quick as a marine engine. I would definitely check the tube size and see if it will take a bigger shaft.

a good header and Tuned pipe will also get you much better performance than a straight exhaust pipe, 2 strokes need that expansion chamber to be able to turn up good rpm's. A good exhaust is one of the biggest performance boosters for a 2 stroke engine.