For the past 18 years we have had 30HP Yamaha outboards on our dinghies. The 30 was chosen for several reasons. First, we like to water ski and this is the smallest engine with which we can drag start on a slalom ski (tricky, but it can be done). The second reason is that this is plenty of power to push the big boat around should we need it in a tight harbor with lots of wind blowing. In effect, this serves as our “thruster”.

There is little difference in weight between this engine at 30HP and some of the smaller engines. It weighs just 109 pounds (49kg), not much more than a 15HP engine. The big difference comes in fuel consumption – at least in theory.

For the 99% of the engine’s life where it is just pushing the dinghy (and not pulling a skier), it is usually running at 1/4 throttle. So the engine loads are light, and fuel consumption is pretty moderate.

On Sundeer and Beowulf we carried 12 gallons of gas for the outboard (47 liters) in two tanks. This was usually enough to last us eight to ten weeks of cruising away from marinas, if we were not skiing. On Wind Horse, with less sensitivity to weight in the ends, we’ve got 30 gallons (116 liters) of gasoline stored in five outboard tanks. Over the recent summer, with about three and a half months at anchor, we used 22 gallons (85 liters). We did a little less exploring than might be the case in the tropics, but this did include water-skiing in Desolation Sound along with our friends Bill and Chris Brees from Pacific Song.

If we were using a 15HP engine, which would be fine most of the time, fuel economy would probably be a little better. But we doubt it would make more than a gallon or so of difference over this time period.

We’ve never had a problem finding outboard gas. But it can be very pricey. So we tend to carry whatever we think we are going to need until we get to the next big city where fuel is usually easier to get and less costly.

If you don’t use up your fuel before putting the outboard to bed for a season, you will probably want to throw out the unused fuel (or give it away). Automotive gas tends to go stale after four to six months and can gum up the fuel metering system of your outboard. It is also a good idea run the outboard while disconnected from its tank, to empty the fuel filter bowl and carburetor.