I converted my ice chest just as you're wanting to do by installing the Frigoboat keel-cooler cooler on my S-38 Mk I. It's simple, quiet, doesn't take up much space, and doesn't draw much power. Next to my autopilot, it's my favorite gadget! And not terribly expensive?
Gerald (Jerry) Brecher
SIRACH 1982 Sabre 38 MK I
Now lying Coruna, Spain
Heading back home to Gloucester, MA this summer 488 Pleasant Street North Andover, MA 01845 USA mobile: 617-510-5133