Yamaha's 300 hp VMax is a 2-stroke engine popular with boaters looking for a higher horsepower package.

The first modern 4-stroke outboard to appear on the boating scene was the 60-hp Homelite in the early 1960s. It was much heavier than the standard 60- hp 2-stroke engines typical of the era, and was slow to accelerate. The Homelite was essentially an inline 4-cylinder Crosley automotive engine standing on end (an orientation it was never designed for). Gas mileage was better than current 2-strokes of similar horsepower, but it also quickly developed maintenance problems.

Just a year or two later Johnson & Evinrude introduced loop charging in a lightweight 3-cylinder 60 hp 2-stroke that was more than 100 pounds lighter. The new 60 had acceleration that blew the doors off the lumbering Homelite, and a tuned exhaust system gave it almost as good gas mileage as the 4-stroke. After a few more years of effort under a new name (Bearcat), the 4-stroke outboard simply faded away due to lack of interest.

It is likely the concept of a 4-cycle outboard would have remained in limbo if the Feds didn't come up with tough model year 2006 exhaust regulations during the middle 1990s. These sounded the final knell for standard 2-cycle marine engines. Faced with the mandate to manufacture an acceptably "clean" outboard that could compete effectively with the 2- strokes during their almost 10-year phase-out, outboard companies really turned up the heat on 4-stroke engineering. The Homelite/Bearcat had already demonstrated that marinized automotive engines can be successfully used in inboard and I/O applications, but they really don't work for outboards where the entire engine is so close to the water and constantly exposed to harsh elements.

As a result, we soon began to see 4-stroke outboards designed from the skeg up for just that purpose. Honda, for example, went completely 4- stroke throughout their entire line. Suzuki, struggling to compete in a cutthroat 2-stroke market, quickly saw the wisdom in going all 4-stroke and now produces very competitive designs all the way up to 250 hp. Suzuki even builds the higher 4-cycle horsepowers for the Bombardier Johnson line. Mercury appears to have more 4-stroke outboards in their line than any other company. It bravely mortgaged the farm to come up with their popular and unique supercharged, smaller displacement Verado outboards that are already available up to 275 hp.Yamaha is developing a complete line of 4-stroke engines too. Each year all of these companies will be reducing 2-stroke models and offering more 4-stroke models. In a few years there will be very few, if any, standard 2-cycle outboards in the U.S. marketplace. It's probably safe to say we'll be seeing 300 hp or larger 4-stroke outboards within a year or two.

It's interesting to note that even in the highly competitive world of outboard motors, a number of manufacturers were quick to realize that the high cost of R&D engineering would be a lot easier to swallow if split 2 or more ways. A prime example is the 2004 4-stroke Mercury 60 that currently hangs on the transom of my flats skiff. Merc developed the basic engine block in conjunction with Yamaha, who also has a similar 60 in the line.

What About The Extra Pounds?

To be sure, even in the 1990s the earliest 4-strokes were both much heavier and much slower out of the hole.Yet they did have good fuel economy and proved durable. These builders were so proud of their efforts that every 4-banger came with a 3-year warranty (as compared to 1-year for the standard 2-stroke outboards). And yes, even from the start the 4-strokes were 10 to 15 percent more expensive. But the payback, even in the days of "cheap" gas, didn't take long. Especially since the average 4-stroke gets 100 hours of run time (between changes) out of three or four quarts of oil, while the standard 2-cycle model will drink quarts of the much more expensive TCW stuff.

On a horsepower-for-horsepower comparison, most of the extra weight comes from the larger cylinder displacement the 4- cycle needed to deliver that same number of ponies. For example, a standard 2-stroke 200 hp V-6 might require only 158 c.i.d. to get the job done, while the equivalent 4- stroke needs more than 200 cubes, or a supercharger for smaller displacements. Add to that the extra engine mass needed to create a sump that holds three to five quarts of oil, and its easy to see where the extra 100 pounds of a 4-cycle comes from.

For the most part, the higher horsepower engines are used by bigger boats, giving the builder some latitude to make adjustments. Moving weight forward easily compensates for the extra pounds on the transom. And a 4-cycle outboard needs about half as much fuel to go the same distance as a 2-stroke. At six pounds per gallon this is a serious weight reduction.

Weight, however, does still remain an issue among the lightweight shallow draft boats which perform best when there's not too many pounds of iron hanging on the transom. I'll get into that in my next column in January. If you have any specific questions please e-mail me at info@boatdigest.com.

See Part I