What length is your Coronado? I have a 1974 23-2 designed by Alan Payne. this company was started by Frank Butler and he later sold and started Catalina. mine is well designed and built. the Yanmar was probably added later, I think in 74 all they were using was Atomic 4. Mine is a shoal draft and great for shallow water, but does sacrifice some upwind ability for the shallow draft.