Outboard type for DS II

Hi All--
After many happy years sailing w/o a motor, I'm taking the plunge and getting an outboard. I have a rubber pad on the transom already. Have read other postings regarding power (I don't need much for my purpose) but would welcome advice on shaft length. Can I get away with a short (15") or should I pay more for a longer one? Thanks, David
After many happy years sailing w/o a motor, I'm taking the plunge and getting an outboard. I have a rubber pad on the transom already. Have read other postings regarding power (I don't need much for my purpose) but would welcome advice on shaft length. Can I get away with a short (15") or should I pay more for a longer one? Thanks, David