If you haven't shopped for an engine in a few years, you may be in for a revelation the next time you visit a showroom: the power plant just isn't what it used to be. The days of simple choices – inboard versus outboard or gas versus diesel – have been replaced by a bevy of options as both performance and price continue to grow.

VOLVO PENTAA quadruple installation of Volvo Penta's IPS pod drive system on a boat built by Lazzara Yachts.

Advances in engine technology, brought about by clean air regulations and the continuing trend toward larger and faster vessels, have resulted in a new generation of engines that deliver more power and fuel efficiency with less noise and pollution. Equally dramatic is that advances can be seen in all segments of the market, from lowly outboard engines to diesel-driven "pod-drive" systems with forward-facing props.

Even Grand Banks, long a standard bearer for traditional design, is debuting a new version of its 41 Heritage EU trawler fitted with the Zeus propulsion system made by Cummins Mercruiser Diesel. The boat will move using computer-controlled pods under the boat, rather than a shaft and propeller.

These modern engines do not come cheap – a four-stroke outboard can cost more than $20,000 – but they boast advanced, computer-controlled technology that is changing the face of marine propulsion. If you haven't been shopping in awhile, or if you are new to the sport, you may want to look at what is coming to market.

OUTBOARD ENGINES

The biggest sellers, and therefore the ones you're most likely to encounter if you are buying a new boat, are the four-stroke motors from Mercury, Yamaha and Honda. Outboards used to be two-stroke motors – like older lawn mowers, which required you to mix oil with gasoline – because they were simple, reliable, lightweight and powerful. But new emissions standards from the Environmental Protection Agency that went into effect in 2006 forced most engine-makers to turn to four-stroke technology, which more closely resemble the engine in your car and make it easier to comply with pollution laws.

MERCURYModern four-stroke outboards, now several years into production, have achieved major gains in performance areas too, in addition to traditional four-stroke characteristics like low vibration and noise levels, smooth running and good fuel mileage.

Theoretically, a four-stroke motor is a more complicated device, but engine makers have so much experience with them in other industries that they can safely be considered a mature technology. Any real problems you have with a four-stroke are more likely to result from something you did wrong – not changing oil, sucking sand into the cooling system in shallow water and the like – than they are from the complexity of the motor.

There is one exception to the four-stroke trend that is worthy of note: Evinrude's E-TEC motors. These are two-stroke engines that use high-pressure injection to finely tune the combustion process, meeting environmental standards while retaining some of the two-stroke's traditional advantages, which are low-end torque – good for acceleration – and top end speed. Evinrude offers the E-TEC in models from 75 HP to 225 HP. The company's other brand, Johnson, covers the lower end of the spectrum, from 9.9 HP to 25 HP.

The ownership differences between an Evinrude two-stroke and any four-stroke mainly involve maintenance. Because a two-stroke engine has its oil mixed in with its fuel, there's no oil and filter to change – though you do have to buy the special two-stroke oil and put that in the tank.