What About Diesel for Smaller Boats?

Yanmar on rack
Small diesels like this stern-drive from Yanmar would make runabouts and deckboats more fuel-efficient, with no sacrifice in cruising or top speeds. Photo courtesy of Yanmar USA.

Look through the classifieds on BoatTrader.com and one thing becomes clear. Big boats burn diesel. Small boats burn gasoline. Why is that?

Yes, I know diesels have the torque needed to push big boats, regardless of whether they’re displacement or planing hulls, but there are significant advantages to using diesels in small boats, fuel efficiency chief among them.

At its annual dealer meeting a couple of years back, Donzi had its 22 Classic in the water for demo rides. The cool thing was that it didn’t have a fire-breathing, rumpity-rump big block under the hatch. It had a small six-cylinder Yanmar diesel in it, with an Arneson surface drive.

I had to drive it. So we hopped in and took it out. Sure, big-block-powered 22 Classics are quicker. Even small-block-powered 22s are more lively. But, they weren’t that much faster. With the little diesel, we got it up to about  65 mph, which is plenty fast in a Donzi 22 Classic.

But here’s something else that sold me. While every other demonstrator boat on the docks had to be refueled at least once a day, the 22 Classic with the diesel never once visited the fuel dock. It was brilliant.

You’d think it would be a case of  “build them, and they will come,” but the little diesels just haven’t seemed to catch on in small runabouts. As the nature of the energy industry changes, the automotive and marine industries will change along with it, so I remain hopeful that we’ll soon see small diesels in the runabout market.

Who knows, maybe recreational boaters will one day get to burn used vegetable oil or even algae-derived fuels. Not only are they renewable, but the fuel-efficiency advantages of diesel engines will still be in place, which  means they’ll go farther on a tank of fuel. That’s an idea we can all get behind.

Brett Becker


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