C22 engines
This is a regularly recurring question. Issues include:
size: where you sail i.e., currents, ocean, lake
type: manufacturers have different throttle and clutch control locations, some like the old style separate, some like (and hate) the integrated new ones
2 strokes are older and less expensive used, 4 strokes are heavier
surroundings: what do other boats of the same size in your area use
You can also do a search on "Catalina 22 engine" or "Catalina 22 engine size" and read what others have written
We had a 7.5 hp Mercury 2 stroke on ours years ago in SF Bay with currents.
The Catalina 25 Association website also is a good resource for outboard engine information:
http://www.catalina-capri-25s.org/forum/