Complete Guide To Outboard Engines - Softcover

Über die Autorin bzw. den Autor

John Fleming has conducted a 60 year love affair with engines and never met one he did not like. There have been a few that were so exciting he remembers them like an old flame but they all serve a purpose and they are all a part of my memories. The first engine he built was a 1948 model, 4.2 horsepower, Champion outboard engine. He was 9 years old which made it monumental task. To see and hold the parts his father had described was fascinating. He held a United States Coast Guard, 500 ton masters ticket and has a total of more than 3,000 days at sea. John has run boats of many types and varieties in 44 States and 3 countries: crossed the Okefenokee in an airboat and canoe, ran the Everglades from Flamingo Park to Chokloskee Island and from Whitewater Bay to the head of the Little Shark River. For eight years he held a State of Florida Teachers Certificate to teach engine repair in the State. John and his wife have run delivery charters across the Gulf of Mexico from Brownsville, Texas to Key West, Florida and up the Atlantic Seaboard as far as Barnegat Bay. They have owned vessels which they have operated for dive charters, fishing charters and towing services. He has written more than 3,500 articles for magazines and newspapers.

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CHAPTER ONE

THE TWO-STROKE / FOUR-STROKE COMPARISON I want to get a few myths out of the way before we get too far into the subject of two-stroke outboards. Just how do they really compare to their four-stroke brethren? Comparisons come in seven important areas, they are physical size, weight, cost, fuel consumption, noise, pollution, and comparative power. First, let us consider physical size. Horsepower for horsepower, the carbureted two-stroke engine is generally much smaller than a four-stroke of comparable horsepower. The fuel injected, two-strokes however require additional accessories to make the injection systems work and they are closer in both size and weight to a four-stroke engine of comparable horsepower. Two-stroke engines with ratings of 25 horsepower and below still have carburetors and they are much smaller than their four-stroke counterparts. The size of the small horsepower four-strokes is causing their owners some problems in small spaces such as outboard auxiliary applications where the engine is in a well. How about weight? The weight comparisons between two-stroke engines and four-stroke engines will vary from horsepower rating to horsepower rating and again by year of manufacture. In some instances the four-stroke engine will be only a tiny bit heavier, in others the difference will be dramatic. There are "niche" engines where the two styles are almost equal in weight. Perhaps the greatest contrast still apparent today lies in the areas of small horsepower engines and very large horsepower engines. In these two areas alone, the two-stroke is dramatically lighter than is the four-stroke. Amongst offshore fishermen and those who need to power dinghies or canoes, the carbureted two-strokes are revered for their smaller, size and lighter weight. Engines in the 2 horsepower to 15 horsepower range are generally considered "portable" when manufactured as two- stroke engines. As a four-stroke engine they no longer are. Four-stroke engines in the 8 horsepower range are about as heavy as you will want to carry. A 5 horsepower, two-stroke engine is about 35 percent lighter than a 5 horsepower four-stroke but this weight advantage does not extend to all comparisons between the two engine types. How about one of those niches where the comparison is closer? Try the Mercury 115 horsepower and 135 horsepower, V-6 engines, with Opti Max injection. Here the manufacturer has de-rated a high horsepower engine, the standard 150, to keep down cost of construction for a smaller horsepower unit! I refer to these de-rated engines as "hybrids." In manufacturing the hybrid engines, Mercury has built a pair of units which very nearly equal a comparable horsepower four-stroke in weight. How close are they? The 115 horsepower, two-stroke, Mercury engine, built on that "V-6" block and employing the Opti-Max fuel injection system weighs well over 400 pounds. This is only a bit less than the four-stroke, 115 horsepower, Honda engine! In fact, it is actually heavier than the 2000 model Yamaha F-115 four-stroke. The introduction of that light Yamaha four-stroke, F-115 constitutes the first time (to my knowledge) that a four-stroke has been lighter than a two-stroke, at any horsepower rating. The high horsepower to weight ratio of those "hybrid" two-strokes limits their use just as similar constraints limit the Honda four-stroke. While this is the only example that I can cite in which a two-stroke engine outweighs a four-stroke of comparable horsepower, it is not the only case where the weights are close. The 135 horsepower, "V-6 Mercury with Opti-Max" fuel injection weighs only a few pounds less than the 130 horsepower Honda four-stroke. Like the 115 horsepower V-6 in the above example, the 135 horsepower V-6 Mercury engine is also built on that same block. Both are "hybrids" to the "V-6" 150 horsepower engine. Remember that these are extreme cases and I cite them only to demonstrate the fact that (A) the weight consideration generally favors the two-stroke engine by a wide margin but (B) it ain't always so! There is another niche to be considered. It is in horsepower ratings above 130 that the two-stroke really starts to pull away. Again, because of certain inherent design characteristics, the two-stroke can stretch the horsepower available from a 480 pound to 500 pound, "V-6" block to much higher levels, with no increase in weight. The four-stroke has no such potential. How about an example? The "largest" two-stroke engine in use today is a 300 horsepower atom smasher from Mercury Marine. This engine weighs about 500 pounds. There is only a small difference in weight between the 130 horsepower, Honda four-stroke engine and the 300 horsepower two-stroke. This is really a terrible disparity with that 300 horsepower two-stroke producing more than twice the horsepower for the same weight. As they are designed today, the four-stroke has no potential to bridge that gap. So much for weight, how about cost? Cost is a very real consideration in this market. Forget the list prices of any engine and concentrate on what you really pay for the delivered unit. Four-stroke engines are much more costly than a matching two-stroke engine. Generally about 35 percent to 50 percent higher.