I'm not sure what a RWC 28hp. is? (raw water cooled?)
A buddy just bought a new Yanmar 30 for 5500.00 to replace his Atomic four. Add new shaft, prop, fuel tank, muffler and hoses ext. I'd bet he's got near seven in it and we did the work.
You start sailing with a bag full of luck and an empty bag of experience. The idea is to fill the bag of experience before you empty the bag of luck.