Eight for C-22 A OK
An eight horsepower outboard is an excellent choice for a C-22, assuming this is a two cycle. A four cycle eight that weights more than 80 pounds would be too heavy. The two cycle eight should with a twenty inch shaft weight close to a two cycle six horsepower with a 20 inch shaft six or about sixty pounds.I would only use a 25 inch shaft if you mount you motor fairly high up.