Engine shaft lengths:
20"
25"
30"
I think the 20' SC's typically had 20" transom cuts, and the 23' had a 25". If you look through some of the transom rebuilds you will see that some guys have decided to move up. For instance FELLOW-SHIP went from a 25" up to a 30" when he rebuilt his Transom. I did the same on my 23'.
Hammer went from a 20" on his 20' to a 25".
http://www.classicseacraft.com/hammers20CCpage2.htm
So to answer the question, if the Transom hasn't been modified you will probably need a 20" shaft motor.
[ October 28, 2002, 09:41 AM: Message edited by: Rich ]