Which Outboard Engine – 4 Stroke or 2 Stroke?
Outboard engines fall into two main categories; 2 stroke and 4 stroke outboards. Both types have their advantages and disadvantages and the type you pick will depend on the intended use. This guide will help you choose which outboard engine is best for your type of boat.
2 Stroke Outboards
2 stroke engines are lighter and faster so when speed and acceleration are required, this would be the engine of choice. 2 strokes are also generally cheaper and keep their value better when it comes to resale. As 2 stroke engines have been around for almost 80 years, parts are readily available, making repairs easy. Also, the design on these engines is less complex than a 4 stroke, meaning problems are less likely to arise.
There are some disadvantages to the 2 stroke engine. 2 stroke engines are more pollutive than 4 stroke engines so they are not so kind on the environment. Their engines are lubricated by the oil that is mixed into the gasoline, meaning the exhaust is smoky and contains unburned oil, which in turn pollutes the water.
With new regulations, outboard manufacturers are looking to find new ways of producing the same power with less pollution.
Some 2 stroke outboard engine manufacturers include Mercury, Nissan, Yamaha and Evinrude.
4 Stroke Outboards
4 stroke engines are quieter, smoother and more economical. Heavier with slower acceleration, they are normally chosen for lakes and rivers. With less pollution and smoke they are also kinder to the environment. If you’re after a quieter, smoother ride, then the 4 stroke outboard is the better choice.
4 stroke outboards are more complicated with more parts so they often require repairs more often. When a repair is required it is usually more expensive and parts are limited.
4 stroke outboards are generally heavier than 2 stroke outboards, so if you own a smaller boat it may not be able to hold the weight of a 4 stroke engine.
Because 4 stroke engines are newer, they are continually being improved to make purchase and repair easier.
Some 4 stroke outboard engine manufacturers include Yamaha, Tohatsu, Suzuki, Nissan, Mercury, Honda and Johnson.
Environmentally Friendly Outboards
If you’re looking for a new outboard, it’s worthwhile considering one of the newer, environmentally friendly models. As well as producing lower emissions, there are a number of other advantages such as better fuel economy, quieter running and reduced operating costs.
The Mechanical Differences Between 2 and 4 Stroke Outboards
The terms “2 stroke” and “4 stroke” refer to the number of times the piston moves during one firing cycle of the engine. In the 4 stroke engine, the four movements, or strokes, are:
Intake stroke: With the intake valve open, the piston moves down allowing a mixture of air and fuel to enter the combustion chamber.
Compression stroke: The piston moves up the cylinder with the valves closed, so that the air-fuel mixture is compressed.
Combustion stroke: With the valves still closed, the fuel is ignited by the spark plug. The explosion pushes the piston down again.
Exhaust stroke: The exhaust valve opens and the piston moves up to push the exhaust gasses out of the chamber so the process can be repeated.
In a 2 stroke engine, there are only two movements of the piston for each combustion; one up and one down:
Combustion stroke: Combustion of fuel drives the piston downwards. As the piston moves down, it exposes an exhaust vent and fuel inlet in the wall of the cylinder allowing exhaust gasses out, and new air and fuel to be sucked in.
Compression stroke: As the piston moves back up, it blocks off the exhaust vent and fuel inlet and thus compresses the air/fuel mixture. The spark plug ignites the air and fuel causing the piston to move down again.
The fuel inlet and the exhaust vent in the wall of the cylinder eliminate the need for valves and the mechanism for opening and closing them which is why 2 stroke engines are much simpler in design.
About the Author
More information on boats and outboards is available from TheYachtMarket.com
Running an antique outboard 1957 Johnson
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1980 JOHNSON OUTBOARD 25HP & 35HP PARTS MANUAL $14.99 |
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Johnson / Evinrude Electric Outboard Service Manual published 1988 $19.99 |
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1976-1979 25 35 hp Evinrude Johnson Outboard Lower Mount Cover Bracket 0320410 $29.99 |
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Johnson Evinrude Outboard Boat Motor 10′ Tilt Trim Cable Extension Kit 174233 $29.99 |
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Starter Drive Gear JOHNSON OUTBOARD 20 20HP 25 25HP 28 28HP 30 30HP 1980-1997 $30.00 |
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Starter Drive Gear JOHNSON OUTBOARD 40 40HP 48 48HP 50 50HP 60 60HP 1980-2001 $30.00 |
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Starter Drive Gear JOHNSON OUTBOARD 65 65HP 70 70HP 75 75HP Bendix 1969-2001 $30.00 |
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1980 JOHNSON OUTBOARD 55HP & 60HP PARTS MANUAL $12.99 |
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Timer Base Johnson Evinrude Outboard 70-75HP 3 Cyl 1993-01 $285.95 |
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Power Pack for Johnson Evinrude Outboard 250 275 300 $234.95 |
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CDI Stator 35 Amp Johnson Evinrude Outboard 185-250HP 93-00 $344.95 |
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Timer Base Johnson Evinrude Outboard 4 Cyl 65-140HP 1978-97 $225.95 |
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Stator 35 Amp for Johnson Evinrude Outboard 200-300 HP $330.95 |
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Drive Shaft 10″ Lower Unit Johnson Evinrude Outboard V8 $135.95 |
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Timer Base for Johnson Evinrude Outboard V6 200 225 HP $252.95 |
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CDI Stator 35 Amp Johnson Evinrude Outboard 185-300HP 88-94 $311.95 |
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CDI Power Pack Johnson Evinrude Outboard V4 65-115 HP 89-97 $122.95 |
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Propeller Shaft Johnson Evinrude Outboard 13 Spline $229.95 |
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Timer Base Johnson Evinrude Outboard 4 Cyl 85-140 HP 78-87 $250.95 |
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CDI Power Pack Johnson Evinrude Outboard V6 235 HP $111.95 |
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Timer Base Johnson Evinrude Outboard 3 Cyl 60-75 HP 84-99 $217.95 |
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CDI Stator 35 Amp Johnson Evinrude Outboard 150-175 88-91 $398.95 |
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CDI Stator 9 Amp Johnson Evinrude Outboard 2 3 4 Cylinder $199.95 |
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Stator 12 Amp for Johnson Evinrude Outboard V4 85-140 $343.95 |
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Timer Base Johnson Evinrude Outboard 120 125 130 140HP 88-99 $249.95 |
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Timer Base Johnson Evinrude Outboard 25-50 HP 92-05 $200.95 |
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CDI Stator 35 Amp Johnson Evinrude Outboard 2 3 4 Cylinder $247.95 |
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CDI Stator 6 Amp Johnson Evinrude Outboard 60-70HP 89-91 $247.95 |
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CDI Stator 9 Amp Johnson Evinrude Outboard 65-115 HP 1988-97 $245.95 |
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CDI Stator 6 Amp Johnson Evinrude Outboard 50-55 HP 2 Cyl $175.95 |
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CDI Stator 9 Amp Johnson Evinrude Outboard 85-235 HP 1978-87 $237.95 |
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CDI Stator 9 Amp Johnson Evinrude Outboard 60-75HP 1979-90 $174.95 |
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1997 EVINRUDE JOHNSON 90HP OUTBOARD REPAIR MANUAL $9.95 |
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1979 JOHNSON OUTBOARD MOTOR 4 HP PARTS MANUAL $19.99 |
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1970 Johnson Outboard Motor Manual 4 HP 4R70 4W70 f $19.99 |
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1970 Johnson Outboard Motor Manual 1 1/2 HP 1R70 Boat f $19.99 |
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1998 Evinrude Johnson 150 175 Outboard Service Manual $29.49 |
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1969-1971 20 25 hp Evinrude Johnson OMC Outboard Exhaust Drive Shaft Housing $19.99 |
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1974-1982 9.9 15 hp Johnson Evinrude OMC Outboard Hood Lever Handle Latch $19.99 |
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evinrude johnson outboard motor 15 18 20 50s 60s fuel inlet $9.99 |
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Starter assy Johnson/Evinrude outboard 1986 4 HP $80.00 |
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Flywheel Johnson/Evinrude outboard 1986 4 HP $55.00 |
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Marine Outboard Cylinder Boring: Johnson, Evinrude $75.00 |
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1954 Johnson Outboard Transom Clamp Assembly 10hp Model #QD-15 $40.00 |
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Power Pac Johnson/Evinrude outboard 1986 4 HP $55.00 |
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Fuel pump assy Johnson/Evinrude outboard 1986 4 HP $50.00 |
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Throttle linka assy Johnson/Evinrude outboard 1986 4 HP $7.00 |
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Exhaust tube assy Johnson/Evinrude outboard 1986 4 HP $30.00 |
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1954 Johnson Outboard Carburetor Assembly 10hp Model #QD-15 $40.00 |
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Armature plate assy Johnson/Evinrude outboard 1986 4 HP $55.00 |
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Teleflex Marine 18-3390 Water Pump Kit $34.64 Sierra Impeller Kit for Johnson / Evinrude. Water Pump Service Kit without housing. Replaces 395060. 85HP (1979-1995), 90HP (1979 and up), 90HP SI, DL (1995 and up), 100HP (1979 and up), 100HP comm. (1984 and up), 105 comm. (1998-2001), 115HP (1979 and up), 115HP SI, DL (1995 and up), 130HP (1997 and up), 140HP (1979 and up), 150HP (1979 and up), 175HP (1993 and up), 200 and 225HP (1993 and up). O… |
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REPLACEMENT IGNITION KEY FOR JOHNSON OR EVINRUDE OUTBOARD ENGINES 1977-1995 MODEL YEARS $12.99 TO DETERMINE YOUR KEY NUMBER, THE NUMBER WILL BE STAMPED JUST BELOW THE KEY HEAD AND THE NUMBERS WILL BE FROM # 51 – 67… |
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Complete Water Pump Kit 25 – 35HP $44.99 Complete Water Pump Kit for Johnson and Evinrude outboard engines. Fits 1996 – 2001 25 30 and 35HP 3 Cyl loopcharge engines. OE# 0437907…. |
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Sierra International 18-7351 Marine Fuel Pump for Johnson/Evinrude Outboard Motor $43.13 Sierra Fuel Pump. 18-7351 Fuel Pumpfeatures: Made To Meet Or Exceed Oem Specifications In Quality And Performance. Heavy Duty Components Assure Long Life. Exact Fit Minimizes Labor Required For Installation. Best Coverage And Availability In The Industry. Replaces: 438… |
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Fishman 910-R AC Adapter for outboard preamps $19.95 Filtered and regulated power supply. 110V only…. |
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TeleflexTrim Gauge (Evinrude/Johnson O/B) $19.31 Smart white and red graphics on a black dial background add a sharp, classic style to any dash. These very low profile bezels follow the curve of the lens to eliminate water trapping. Scratch-resistant domed glass lenses shed water. Through-dial and perimeter lighting provides excellent readability at night. Requires 2-1/8′ dia. hole…. |
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Martyr OMC/ Johnson/ Evinrude Outboard Anodes CM392462Z Small Horse Shoe Martyr zinc anodes to fit Johnson, Evinrude, and OMC Bombardier outboard engines. Choose from small block, waffle bar, anode wedge, half moon, horseshoe, anode block, curved block, long bart power T, and anode plate shapes to suit your outboard engine corrosion protection application…. |
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Johnson Pumps of America 28572 Marine Pump Cartridge for 750 GPH Motor $19.32 Mayfair’s Bassperator II Series Aerator Pumps feature removable motor cartridges allowing anglers to quickly change the pump capacity to accommodate different bait or to make a quick replacement. The procedure is quite simple, just lift the tab, turn the motor housing, and pull the motor out. It only takes a few seconds, and installing a new motor is just as easy…. |
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McGard 74039 Marine Propeller Lock Set (3/4- 16 Thread Size) – Mercury/MerCruiser/OMC – Set of 1 $70.96 McGard Propeller Locks. Keep your boat safe from sticky – fingered vultures! Outstanding CLOSE – OUT PRICE! You spend your hard-earned money to keep your boat in tip-top shape… why allow a petty thief to rip off a part of your beautiful watercraft? This McGard Propeller Lock keeps your propeller collar stationed in place so gripping tools and other methods of removal are thwarted! Made of naval … |
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Teleflex Marine 18-7823 Fuel Pump Kit $8.88 Sierra 18-7823 Johnson/Evinrude Fuel Pump Kits. Replaces OEM part # OMC 393088…. |
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Evinrude/Johnson Outboard Shop Manual $26.09 Evinrude/Johnson Outboard Shop Manual |
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Evinrude Johnson Outboard Shop Manual $26.09 Evinrude Johnson Outboard Shop Manual |
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Clymer Evinrude/Johnson Outboard Shop Manual $26.09 Clymer Evinrude/Johnson Outboard Shop Manual |
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Sierra Thermostat Kit For Johnson/evinrude Outboard Motors $31.99 Sierra Thermostat Kit For Johnson/evinrude Outboard Motors . Thermostat Kit for Johnson/Evinrude Outboard Motors |
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Sierra Thrust Washer For Johnson/evinrude Outboard Motors $43.99 Sierra Thrust Washer For Johnson/evinrude Outboard Motors . Replaces: OMC 320305 |
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Sierra Prop Shaft For Johnson/evinrude Outboard Motors $579 Sierra Prop Shaft For Johnson/evinrude Outboard Motors . Replaces: OMC 386659 |
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Sierra Power Pack For Johnson/evinrude Outboard Motors $109.99 Sierra Power Pack For Johnson/evinrude Outboard Motors . Replaces: OMC 583748 |
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Sierra Thermostat 140 For Johnson/evinrude Outboard Motors $25.99 Sierra Thermostat 140 For Johnson/evinrude Outboard Motors . Replaces: OMC 434137 |
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Sierra Thermostat 143 For Johnson/evinrude Outboard Motors $13.99 Sierra Thermostat 143 For Johnson/evinrude Outboard Motors . Replaces: OMC 436195 |
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Sierra Outboard Ignition Coil Johnson/evinrude $33.99 Sierra Outboard Ignition Coil Johnson/evinrude . Fits Johnson/Evinrude 50 to 135hp from 1971-75. |
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Seloc’s Johnson/Evinrude Outboard $29.08 SELOC Marine maintenance and repair manuals offer the most comprehensive, authoritative information available for outboard, inboard, stern-drive and diesel engines, as well as personal watercraft. SELOC has been the leading source of how-to information fo |
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Evinrude/Johnson Outboard Shop Manual 48-235 Hp, 1973 1990 $26.09 Evinrude/Johnson Outboard Shop Manual 48-235 Hp, 1973 1990 |
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Evinrude Johnson Outboard Shop Manual 1.5 to 125 Hp 1956-1972 $26.09 Evinrude Johnson Outboard Shop Manual 1.5 to 125 Hp 1956-1972 |
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Sierra 18 3203 Impeller Repair Kit For Johnson/evinrude Outboard Motors $19.99 Sierra 18 3203 Impeller Repair Kit For Johnson/evinrude Outboard Motors . Impeller Repair Kit for Johnson/Evinrude Outboard Motors |
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Sierra Lower Unit Assembly For Johnson/evinrude Outboard Motors $3469 Sierra Lower Unit Assembly For Johnson/evinrude Outboard Motors . Lower Unit Assembly for Johnson/Evinrude Outboard Motors, replaces: OMC 5004632 |
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Sierra 18 3202 Impeller Repair Kit For Johnson/evinrude Outboard Motors $19.99 Sierra 18 3202 Impeller Repair Kit For Johnson/evinrude Outboard Motors . Impeller Repair Kit for Johnson/Evinrude Outboard Motors |
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Sierra 18 9125 Oetiker Clamp Kit For Johnson/evinrude Outboard Motors $249.99 Sierra 18 9125 Oetiker Clamp Kit For Johnson/evinrude Outboard Motors . 18-9125 Oetiker Clamp Kit for Johnson/Evinrude Outboard Motors |
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