No outboard is going to work great
on a small light boat in a steep chop.
But adding lots of horse power is not likely
to help much either.
A 4 stroke 6HP long shaft motor will work
fine, and at 55lbs it will be possible to
lift it on and off the transom without
herniating a disk.
The Suzuki 5 used to be the standard
engine for Olson 30s, and they could
get up to 7 knots out of that motor.
I had a Coronado 25 which I consider to be somewhat small.
It had a good well layout with the motor mount somewhat
forward of the water line, IIRC. With the long shaft, at that time
20", I think, the prop almost never came out of the water and then
just barely. Adding HP for nasty conditions is OK if you can
"get the power to the ground" so to speak. A lot depends on
your transom or well layout. I would think the new high thrust
props with lower gearing and 25" shaft would be far more
efficient than the older standard props. We got a prop with
about an inch or so less pitch and it worked fine. Running
in calm water is one thing, going against the wind and steep,
high chop is another. Power is good.