Parts of a Boat Engine
The parts of a boat engine are very similar to those of a car engine. In fact, most boat engines are manufactured by companies like Chevrolet and Ford. To understand the parts of a boat engine and what action each part performs, it is best to familiarize yourself with the different systems on the engine.
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Ignition
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The purpose of the ignition system is to ignite fuel. When fuel burns, power is created. When you turn the key to start the boat engine, electricity flows from the battery through a voltage regulator and into the coil. The coil stores the energy until it reaches up to 100,000 volts. At just the right moment, during the compression stroke in a particular cylinder, the coil releases high voltage through the plug wires to that spark plug. The spark ignites the fuel in the cylinder and drives the piston down for the power stroke.
All this is timed by the rotation of the cam shaft raising and lowering the intake valves. A belt from the cam shaft turns a device inside the distributor in perfect time with the intake valves and piston stroke. If any of the ignition systems parts fail---the voltage regulator, the coil, the distributor, plugs, wires, or timing---the engine runs poorly or not at all.
Fuel Delivery
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The purpose of a fuel delivery system is to mix air and fuel and meter that mixture to the cylinder for ignition. There are two types of fuel delivery systems that can be used in a boat engine: a carbureted system or fuel injection. They both serve the same purpose. When a piston pulls downward in the cylinder, the intake valve is open and air is sucked into the intake manifold. Fuel is mixed with the air as it passes through the opened valve into the cylinder. As above, this process is all controlled by the timing of the cam shaft.
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Compression
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When the spark ignites the fuel, the cylinder must not leak any of the power. The rings around the piston must press against the cylinder walls precisely. The valve seats must fit exactly in their guides. The timing must be exact. If any of these parts are worn or damaged, the engine will not run at full power.
Cooling
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The cooling system on a boat engine is very different than that of an automobile engine. Raw water is pumped directly from the body of water in which the boat sits. The water flows into the engine block's water jacket and is circulated by the water pump. From there it flows into the risers. These are specialized devices that mix exhaust with the water. At this point, the exhaust forces the hot water back into the lake.
Location of Major Boat Engine Parts
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The head(s) sit atop the engine block. Heads contain the intake and exhaust valves. Pistons within their cylinders are inside the engine block. Parts of the block are hollow to allow cooling water to circulate. The risers sit beside the heads and act as exhaust manifolds.
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