An important decision in any powerboat project is the choice of exactly what powertrain to use. Our Starwind 860 is now almost at the point where that decision must be locked in.

Should it be an inboard or an outboard? Gasoline or diesel? What kind of propeller?

And, importantly, why?

With the recent release of the final report of Nigel Calder's HyMAR project, marine internal combustion / electric hybrid powertrains are making waves once again- and not necessarily in a good way, as Calder's team found that the benefits of the expensive hybrids were limited to a relatively narrow, low-speed operating regime. We've known for quite a while that the major advantages of gas/electric and diesel/electric hybrid cars- namely, instant start/stop and regenerative braking- don't apply to boats. We've also known for quite a while that hybrid systems only make economic sense aboard ship if the house loads are comparable to, or larger than, the power required for main propulsion.

Tech addicts need not fear, though: There are many other fuel-saving and pollution-reducing technologies waiting in the wings, and hybrids aren't quite out of the running yet.

Every year, mixed in with the usual chatter around the boatyards, I hear at least a few comments along the lines of "I beefed up the transom of my 14-footer so it can take 60 horsepower!"

Er, no. That's not how it works.

Maximum power ratings for small outboard vessels are calculated according to the size and design of the boat, taking into account the following factors:

• Length of hull (longer = higher power rating)
• Beam at transom (wider = higher rating)