18 BASIC POWERBOATING. SAFETY & RESCUE FOR SAILING INSTRUCTORS Outboard Cooling System
Most outboard motors are water-cooled. The illustration tracks the flow of cooling water which enters through the cooling water intake, is pushed up the water feed tube by a water pump, and then circulates through waterways in the engine block. The water then flows back down the leg where it mixes with the exhaust gases and exits through the propeller hub. During its journey through the engine, a bit of the cooling water is diverted through the inspection outlet for cooling water discharge, to let you know that the cooling system is working. Outboards smaller than five horsepower will usually have their exhaust outlet located just above the propeller, instead of through the propeller hub.
Fueling
Procedure for Two-Stroke Outboards. Oil is mixed with the fuel to lubricate the engine and there are two ways this can be done. To determine which method applies to your outboard, check the manufacturer’s manual. 1 Adding oil to the fuel tank. This method is most common in older engines. Oil is usually added first, followed by gasoline to mix the ingredients. If the fuel tank is empty, add a gallon of gasoline before adding the oil, then add the rest of the fuel. Many outboards use a ratio of 1 pint of oil to 6 gallons of gasoline, but check the manufacturer’s manual for the recommended ratio. Serious damage to the engine can result by using an improper mixture.
2 Adding oil to the oil tank. Many newer two-stroke outboards have oil tanks (either as part of the engine or separately) that automatically meter the oil into the gasoline according to the engine speed.
Procedure for Four-Stroke Outboards. These run on gasoline, with the lubricating oil added separately to the crankcase.
No matter what type of outboard is used, it is very important that you use the type of oil recommended in the manufacturer’s manual.
Safety Precautions for Fueling. Always remember that gasoline vapor is heavier than air. It can settle in bilges or enclosed compartments, and a spark can ignite an explosion.
Outboard Cooling System
Water circulates through the engine’s waterways.
Water pump propels the water up and through the cooling system.
Water flows through the cooling water intake.
Water exits
through inspection outlet.
Water exits through the propeller hub.
Outboard Fuel System Fuel line connector
Fuel line
Fuel
Primer bulb
gauge Tank
Fuel line connector
Air vent must be open for fuel to flow to the outboard motor. If closed, the motor will not start or it will stop after running a short time. Vent is usually closed when a boat is not being used.
Table of Contents
Tank cap with air vent
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