Since no one responded, I'll give it a try.
I'm confused. You have the boat, right? Why not just take the hose off either the raw water strainer or the pump and measure it?
IIRC, Catalina used 1/2" seacocks, but the hose off the top of the strainer could be 5/8".
The pumps do not dictate the hose size, since the pump comes with threads into which is screwed the barb adapter, like this:
http://c34.org/bbs/index.php/topic,6766.0.html