What Goes Into an Outboard?
The Powerhead is the actual engine of the outboard. The powerhead may be either a 2-stroke or 4-stroke. At the top of the powerhead is the flywheel. The flywheel's momentun keeps the internal powerhead components moving smoothly between powerstrokes. The flywheel also contains magnets which are used to provide energy for the ignition and electrical systems.
The flywheel is attached to the crankshaft. The crankshaft converts the movement of the pistons into rotating motion. Connecting rods attach the pistons to the crankshaft. Each piston moves back and forth in a cylinder.
At the rear of the powerhead are 1 OR 2 cylinder heads containing one spark plug for each cylinder. Models with 1 cylinder head are called inline because all cylinders are in one line.
On 4 stroke models the cylinder head also contains the intake and exhaust valves. Many 4 stroke engines have fuel injectors mounted near the intake valves. 2-Stroke engines with direct fuel injection have injectors mounted on the cylinder head.
At the front of the powerhead is the air lencer. Behind the air silencer are the carburetors if the outboard has them. On fuel injected models, air enters the powerhead through one or more throttle bodies.
The exhaust housing is the largest component of the midsection. It contains cooling and exhaust passages. Stern brackets are used to mount the outboard to the boat. Many models have a power trim and tilt unit mounted between the stern brackets.
The steering arm assembly rotates in the swivel bracket. Connecting the top of the stern brackets with the swivel bracket is the tilt tube. The outboard pivots around the tilt tube when operating the trim and tilt. Steering cables are often attached to the tilt tube.
Rubber mounts help to dampen vibration from the outboard so it is not transmitted to the boat.
The driveshaft passed through the midsection -It transfers power from the crankshaft to the gearcase. The gearcase is attached to the bottom of the midsection. It transfers the vertical rotation of the driveshaft to the horizontal rotation of the propeller through a set of gears.
The gearcase contains water intakes to supply water for the outboard's cooling system. This part of the gearcase housing is called the anti-ventilation plate. It helps prevent air from being drawn into the path of the propeller causing it to lose thrust. At the bottom of the gearcase is the skeg. The skeg helps protect the propeller from damage due to striking an underwater object. It also enhances the ability to steer the boat.
Mid Section :
Test Your Knowledge: