Hi there, have a Markham Whaler 4.2. Twin 35s that are just about stuffed. In other words they are stuffed. Would like to replace them with a single 70-80 H.p E-tec centre mounted. This would save the hassles of 2 engines. How do these things perform on a single engine. I know they are not designed for it. The websters Twin fishers were, but they spent a lot of time getting it right.