Single Engine or Twin Engine ?

People like twin engines on boats because they can’t pull over to a service station if one quits. That’s a big reason for having two motors, particularly on offshore boats. However, the excess factor has to be weighed against a lot of other factors when you decide whether to have one engine or two. The most obvious factor is cost. Outboard motors are outrageously expensive, averaging from $10,000 to $20,000 for a V6 of 150 to 225 horsepower. Buying two motors instead of one can add 30 percent to the price of a boat.

Inboards and stern drives are similarly costly. Two engines also burn a lot more fuel—basically twice as much, although you may go faster. If you go with two motors, choose them so that each motor can plane your boat. You may have to buy somewhat larger motors to have this capability, but it’s money well spent when you really need that extra power 50 miles offshore and want to come home at 25 mph instead of 5. Twin engines have the added advantage of making for easy steering around the docks.

With two motors, the same redundancy that’s good in terms of dependability is bad in terms of maintenance. If you run aground, there are 2 props and 2 lower units to repair. There are 12 spark plugs instead of 6, 2 batteries to keep charged instead of 1, and so on. Twin engines provide security when you head offshore. If one breaks down, the other will bring you home. However, if you’re pinching to buy a boat in the first place, that second engine may put you way over the top.

Is one big engine better than two small ones? Could be, if you’re interested mostly in speed. A pair of 90s won’t usually match a single 200 and maybe not even a 175, because the single has less drag due to there being only one lower unit. It’s also much less expensive to buy one big single rather than two smaller motors that put out an equivalent power combined.

One popular approach is to use a single main engine, and also carry a “kicker” or smalllow-horsepower outboard for emergency low-speed propulsion. The power you choose for your boat depends on the “mission” you hope to pursue. Balance the initial costs, fuel economy, and dependability factors when you make a selection. Fortunately, nearly all modern engines are far more dependable and more fuel-efficient today than they were just a few years back.

Few things you need to know :

• Two-cycle outboards are the usual motor for most beginning recreational boaters.
• Outboards, stern drives, and inboards are suited to different boats and boating needs.
• Most motors deliver their best economy at three-quarter throttle.
• Single engines are more economical than twin engines, but twins provide more security.