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Overview
This book starts with the difference in design and power between the two-cycle outboard and its new brother, the four-cycle outboard.
As with John's, Complete Guide To Gasoline Marine Engines, these pages take the reader deep inside the engine by discussing the design, function and results of the entire engine system and drive unit. The book's design allows the reader to start with the basics and progress through each skill level until a thorough understanding of engines is achieved.
This book also delves deeply into the technical aspects of outboard engines, but the information remains extremely easy to understand and follow throughout each step.
You will not find another book that will explain outboard engines as completely or easily as this book.
One fact remains; when you have read, The Complete Guide To Outboard Engines, you will be the most popular person on the dock every Saturday morning.
Illustrated
Product Details
| ISBN-13: | 9781892216311 |
|---|---|
| Publisher: | Bristol Fashion Publications |
| Publication date: | 09/05/2000 |
| Edition description: | Spiral |
| Pages: | 188 |
| Product dimensions: | 5.50(w) x 8.50(h) x 0.43(d) |
Read an Excerpt
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.
Table of Contents
- INTRODUCTION
- CHAPTER ONE
- TWO-STROKE/FOUR-STROKE COMPARISON
- CHAPTER TWO
- WHAT DOES THE ENGINE DO?
- CHAPTER THREE
- CYLINDER BLOCK & CYLINDER HEAD
- CHAPTER FOUR
- ROTATING ASSEMBLY
- CHAPTER FIVE
- RECIPROCATING ASSEMBLY
- CHAPTER SIX
- HOW TO BALANCE THE ENGINE
- CHAPTER SEVEN
- IGNITION SYSTEMS
- CHAPTER EIGHT
- THE CARBURETOR
- CHAPTER NINE
- FUEL INJECTION
- CHAPTER TEN
- TWO-STROKE VALVES
- CHAPTER ELEVEN
- LUBRICATING SYSTEMS
- CHAPTER TWELVE
- EXHAUST SYSTEM
- CHAPTER THIRTEEN
- HOW THE ENGINE RUNS
- CHAPTER FOURTEEN
- FLAME PROPAGATION
- CHAPTER FIFTEEN
- MECHANICS OF TWO-STROKE ENGINES
- CHAPTER SIXTEEN
- ENGINE DESIGN
- CHAPTER SEVENTEEN
- PAN, COWL & DRIVE SHAFT HOUSING
- CHAPTER EIGHTEEN
- GEAR CASE
- CHAPTER NINETEEN
- PROPELLERS
- CHAPTER TWENTY
- SETUP THE ENGINE
- CHAPTER TWENTY-ONE
- A MEASURE OF EFFICIENCY & PERFORMANCE
- CHAPTER TWENTY-TWO
- TROUBLE SHOOTING
- CHAPTER TWENTY-THREE
- A BIT OF HISTORY
What People are Saying About This
Mark Klossner, Mercury Marine Dealer Training Manager, Mercury University:
Bravo to John Fleming for translating the technical jargon of marine propulsion in a way that’s easy for everyone to understand. His three books, Complete Guide To Outboard Engines, Complete Guide To Gasoline Marine Engines, and Complete Guide To Diesel Marine Engines are well-written, thoughtfully laid out and very informative. They should be required reading for anyone who owns, fixes or sells marine engines!
Interviews
From the Author
The outboard engine gets its name from the fact that it is mounted "Outboard" on the transom of the boat. On some vessels there may be extended "brackets" for mounting the engine. Certain ones of these extended brackets may be able to raise or lower the elevation of the engine. They are called "jacking plates."
The outboard engine can be anything from mild to wild. It can troll at one mile per hour and five hundred RPM. It can run over 150 miles per hour and on occasion, I have seen them turn in excess of 15,000 RPM. The choice of type and purpose for which the engine is used are strictly up to you. The fisherman can travel in a silence that permits deep meditation and the racer can run at speeds that raise the hairs on your neck, all with a two-stroke engine. A six cylinder, two stroke engine, turning 9,500 RPM, produces 57,000 explosions per minute!
The sound is like all the little hounds from hell, turned a loose at once. The speed of a hydroplane is intoxicating like a fine wine, but it is dangerous, and it is expensive. In this book we will tell you about all of them, the fast and the not so fast.
Of course, the outboard mounted engine may have a two-stroke or a four-stroke power head. In fact, the lower units or gear cases are essentially the same for either engine. The mounting brackets and tilt/trim units are, for the most part, identical. The midsection and the power heads for the two-strokes are different.
It is an understanding of the two-stroke cycle mystique which prompts this book, however, and to that end we will pursue two-stroke technology. The two-stroke power head is in a state of flux. Some say it is on the way out, butdo not write it off just yet.
At a recent test site where we were testing pontoon and deck boats an engineer from Mercury Marine suggested that a "possible alternative" to the four-stroke engine was suggested by the new clean burn outboards using Opti-Max technology.
His point, and one well taken, was that it is easier to pursue one type of power head and one technology than to try to develop engines in two separate styles. It is also cheaper. This approach seems sound and practical if the EPA requirements can be met. Mercury engineers have a way of making the difficult seem entirely plausible.
Pollution laws certainly do not favor the two-stroke as it has been configured in the past, for it has been an inherently dirty engine. Direct Fuel Injection (DFI) may well clean up and extend the life of the two-stroke engine. Other technologies, only hinted at by the manufacturers, may give it life anew.
The lack of any practical four-stroke power heads in the upper horsepower classes, engines of 150 horsepower and above, makes that two-stroke a necessary commodity. High cost and excessive weight on existing engines has further conspired to delay the invasion of the four-stroke outboard. Before they totally displace the two-stroke engine they have much to prove.
Regardless of what may be contained in the final chapter of the two-stroke story, I for one, shall never forget the engine. It is almost as much a part of me as an arm or leg and it has provided me with memories that I will take to the grave.
It was on the Tensaw River of Alabama that I first ran a 5 horsepower, 4 cylinder, opposed piston, Evinrude outboard engine that belonged to my father. There were so many fish then that no one can describe the situation. You would just have to be there.
I spent many quiet hours on that river and then one day I climbed into my first hydroplane. It was a Fillinger "D" boat. I took one look at that rooster tail and I was forever hooked. I still love the sound of a high-winding engine when it is running right at the edge of the possible.
Stay with us and we will tell you all about two-strokes, how they run, why they run, and why sometimes they do not run! One chapter and a few references to four-stroke outboards will be made in this book but they will only be for comparison purposes.
—John Fleming