Tom:

This is a purely theoretical answer as I don't have a W42, but the John Deer 4045D would be a nice engine to install in this boat. It is an 80 hp, modern, all mechanical, non turbocharged design with a balance shaft for smoothness. It has a bit more displacement, but is a bit lighter than the 85 hp 4-236 Perkins that was often installed in W42s.

David