Engine Acceleration Is Poor; Troubleshooting With Vacuum Gauge - Mercury 305 CID Service Manual

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Engine Acceleration Is Poor

Also refer to "Poor Boat Performance"

Idle mixture screws

Incorrect ignition timing

Incorrect distributor or amplifier advance curve

Accelerator pump

Cracked or dirty distributor cap or rotor

Float adjustment

Dirty carburetor

Low compression

Steady reading between 15-21 inches at idle

Extremely low reading, but steady at idle RPM

Fluctuates between high and low at idle RPM

Fluctuates 4 or 5 inches very slowly at idle RPM

Fluctuates rapidly at idle, steadies as RPM is

Continuously fluctuates between low and normal

reading at regular intervals at idle RPM

90-823225--1 1096

Special Instructions

Refer to Section 4B

Check for stream of raw fuel from accelerator

pump discharge nozzle, when opening throttle

with engine shut off

Intake manifold or carburetor base

Fouled, burned; wrong heat range; cracked

Vacuum leak; incorrect timing; underpowered

boat; faulty boat bottom

Blown head gasket between two adjacent

Carburetor needs adjustment; spark plug gap

too narrow; valves are sticking

Valve guides are worn

Burned or leaking valve

TROUBLESHOOTING - 1C-17

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