The Honda 135's are identical to the Honda 150'. Except for variable valve timing, which kicks in above 4200 rpm. On Journey On, I usually stay below that, ~3800 rpm. So essentially, I'm running a 135.
The only reason I got a 150 was because of resale. Everybody would say: "oh, it's a 135, that's underpowered." As is happening here. The 135's are enough.
By the way, the Catalina Twin Harbour harbor patrol use 150's, even though they never actually go anywhere. 99% of the time they're idling, the other 1% they're going 5 knts.
One additional comment. That C-dory 24 would be great for the Channel Islands. We've gone over in boats from 22' to 36'. It's not the trip over, it's the swells in the anchorage, and a catamaran should be a lot better than a monohull. Any C-dory is sturdy enough, but remember it's only 25' long.
Boris