YAMAHA MODULE 8:LOWER UNIT EXAM QUESTIONS AND ACCURATE
ANSWERS 2024/2025 | VERIFIED
Exhaust tuner, muffler, and oil pan - Mid section parts
Exhaust tuner - Main exhaust gas passage
Muffler - Cools exhaust gases at high and low speeds
Muffler - Area that also functions as a noise reducing path for the exhaust gases
Oil pan - Cools the motor oil through Easter passages around the exhaust tuner
Drive shaft - Begins at crankshaft and connects all the way thru mid section and then to the gears
in lower unit
Water pump - Part of lower unit but sits in mid section
Discharged - At low speeds, some of the water is what thru idle relief port
Increasing exhaust flow - At higher speeds, the boat and motor rise out of the water and get on
plane, increasing what
Propeller hub - When exhaust flow increases, some of the cooling water flows out of where
Exhaust at slow speed flows thru idle silencer; - 2stroke has what type of cooling system at slow
speeds
Exits thru lower unit - 2stroke: At high speeds, what type of cooling system is involved
, Vast majority of exhaust gases are rotted and expelled through the motors propeller hub - Most
late generation outboards utilize a propeller hub exhaust design where....
1. A negative pressure is created at the prop hub that assists with the flow of exhaust gases
2. Releases the exhaust (and noise) relatively deep in the water and is therefore very effective at
minimizing noise - The propeller hub exhaust design performs what functions
Forward of the propeller blades - During high thrust reverse operation, exhaust gas does not pass
thru the hub, but escapes from where
Keeps rotating blades free of agitated or disturbed water, which minimizes propeller slip and maximizes
reverse thrust - The high thrust motor system does what for the prop
Prevents the rubber dampened hub of the propeller from being overheated and damaged by the passing
flow of hot exhaust gases - Some of the larger high thrust larger outboards feature a trim tab
system that prevents what
Thermostat - Open and close based on water temp and regulate how much water is flowing thru
the cooling system
1. When Water In cooling system is cold, a spring will hold thermostat closed
2. As the motor is running, water in the cooling system begins to heat up
3. Once the water reaches a predetermined temperature, the wax will begin to expand and force
thermostat open
4. This allows hot water to flow out of the motor and cool water can begin to circulate - Explain
Thermostat process
Ensures that fresh cool water is circulated throughout the motor when it is running - Purpose of
water pump
Gear system, propeller shaft, propeller, propeller shaft, water intake port, and various control surfaces -
Lower unit is made up of what
ANSWERS 2024/2025 | VERIFIED
Exhaust tuner, muffler, and oil pan - Mid section parts
Exhaust tuner - Main exhaust gas passage
Muffler - Cools exhaust gases at high and low speeds
Muffler - Area that also functions as a noise reducing path for the exhaust gases
Oil pan - Cools the motor oil through Easter passages around the exhaust tuner
Drive shaft - Begins at crankshaft and connects all the way thru mid section and then to the gears
in lower unit
Water pump - Part of lower unit but sits in mid section
Discharged - At low speeds, some of the water is what thru idle relief port
Increasing exhaust flow - At higher speeds, the boat and motor rise out of the water and get on
plane, increasing what
Propeller hub - When exhaust flow increases, some of the cooling water flows out of where
Exhaust at slow speed flows thru idle silencer; - 2stroke has what type of cooling system at slow
speeds
Exits thru lower unit - 2stroke: At high speeds, what type of cooling system is involved
, Vast majority of exhaust gases are rotted and expelled through the motors propeller hub - Most
late generation outboards utilize a propeller hub exhaust design where....
1. A negative pressure is created at the prop hub that assists with the flow of exhaust gases
2. Releases the exhaust (and noise) relatively deep in the water and is therefore very effective at
minimizing noise - The propeller hub exhaust design performs what functions
Forward of the propeller blades - During high thrust reverse operation, exhaust gas does not pass
thru the hub, but escapes from where
Keeps rotating blades free of agitated or disturbed water, which minimizes propeller slip and maximizes
reverse thrust - The high thrust motor system does what for the prop
Prevents the rubber dampened hub of the propeller from being overheated and damaged by the passing
flow of hot exhaust gases - Some of the larger high thrust larger outboards feature a trim tab
system that prevents what
Thermostat - Open and close based on water temp and regulate how much water is flowing thru
the cooling system
1. When Water In cooling system is cold, a spring will hold thermostat closed
2. As the motor is running, water in the cooling system begins to heat up
3. Once the water reaches a predetermined temperature, the wax will begin to expand and force
thermostat open
4. This allows hot water to flow out of the motor and cool water can begin to circulate - Explain
Thermostat process
Ensures that fresh cool water is circulated throughout the motor when it is running - Purpose of
water pump
Gear system, propeller shaft, propeller, propeller shaft, water intake port, and various control surfaces -
Lower unit is made up of what
