Outboard motor characteristics

Posted by admin in Outboard Motor on 10 26th, 2008 | no responses

Outboard motor characteristics: Cycle type:

• 2-Stroke: cycle consists of 2 strokes by piston:
  up is exhaust/compression stroke,
  down is power/intake stroke.
• 4-Stroke: cycle consists of 4 strokes by piston:
  up for compression stroke,
  down for power stroke.
  up for exhaust stroke,
  down for intake stroke.

4-stroke design uses valves, separate lubrication system.
2-stroke design uses cylinder ports, oil mixed into fuel.

2-stroke gives more power for same weight, but consumes more fuel and generates more pollution and noise, has less low-end torque.

Fuel system type:

• Carbureted: air is sucked through a venturi, gas is sucked in to mix with it, then mixture goes to cylinder.
  May be one single-barrel carburetor per cylinder, or one two-barrel per two cylinders.
• Fuel-injected: fuel is sprayed into cylinder, or chamber that feeds to cylinder. Mixes with air in the cylinder.
  May be single-point or multi-point injection. May be electronic (injects into intake manifold) or direct (injects into cylinder; better).

Most small 2-stroke outboards use carburetors.

Ignition system type:

• Flywheel magneto with breaker points.
• Flywheel magneto without breaker points (aka “solid-state”).
• Capacitor discharge. Gives higher voltage.

Note: spark plugs are not properly gapped when you buy them; you have to set the gap.

Engine cooling system type:

• Water-cooled.
• Air-cooled. Noisy.

Some Honda’s have water-cooled propeller shaft but air-cooled engine.

• Electric-start or manual pull-start ?
• DC output (useful for running navigation lights) ?
• Shaft length.
• Internal or external fuel tank ?
• Weight.
• Horsepower.