How big a kicker needed?

[bmajvi]

+1 on the torque advice. Also depends on if you really need it to push the boat into decent sized seas, wind and current, or just in benign conditions. I've been aboard a 40' sailboat with a dead auxiliary engine that did remarkably well with a small RIB strapped alongside with just a 4hp outboard - but that was in sheltered water with pretty light breeze. Lotsa 20-30' sailboats use 9.9 hp outboards as their auxiliary motor