not much help, but...
When I was searching for another boat 3 years ago, I looked at several used diesel Catalina 25's. All had fixed keels. Most of the outboard versions I have sailed had swing keels. My guess is that the swing keel trunk takes up too much room to allow room for a diesel, but that is just a guess. FYI, a 9.9 outboard will push a 25 along at 6 knots without struggling, will give you more storage and will be easier to deal with when repairs are needed. I like the diesel I have now, but sometimes long for the simplicity of a 4 stroke outboard. Good luck.
