81 Catalina 38 '''' Sparkman Stevens
While the horspower rating is a major factor to concider, it''s the PROP that gets the power to the water. On many of these racer/cruiser designs, a feathering Martek was the standard. These props, when folded give little or no drag. Great when racing, however they have reduced "push" when in forward and will downright scare you in reverse! If you are mostly cuising, go for a PROPERLY sized three bladed fixed prop. The formula for sizing a prop can be quite intimidating and is usually best left for the professionals. Although I recall a good article from Sail Magazine a few years ago that shed some light on the process. And remember, hull speed is a major limiting factor, once hit, a displacement hull takes a huge increase in power to go beyond it, so with a good three blade prop, your 25hp should be sufficient.
The Catalina 38 is a really nice sailing boat. IMHO, superior to many of today''s floating motels. Back then, IOR was the International OCEAN Racing formula, where boats were expected to compete in long distance off-shore races. The "Squirely" running before the wind problems were more when the wind was 25kts+ and you were carrying your 1.5oz radial ''chute in large (8''+) following seas. Plan on doing any of that?
Good luck, hope this helps!