Charging System Inoperative?

  Loose or broken drive belt
  Engine RPM too low on initial start, ( Rev engine to 1500 RPM)
  Loose or corroded electrical connections
  Faulty battery gauge   ( Best way to test, try another gauge)
  Battery will not accept charge ( see Battery Test Section)
  Low electrolyte or failed battery
  Poor ground to alternator (Don't trust the bracket)
  Faulty alternator or regulator

Engine Runs Poorly At Idle?

  Clogged flame arrestor
  Improper idle fuel mixture adjustment
  Engine floods at idle, (Bad needle and seat, float level off)
  Problem in ignition system causing the engine to run rough
  Idle mixture screw adjusted incorrectly
  Incorrect float level drop
  Moisture on ignition components (Cap or spark plug wires arcing)
  Water in fuel
  Low grade or stale fuel
  Incorrect ignition timing
  Automatic choke ( not opening )
  Spark plugs Fouled, burned, cracked porcelain
  Spark plug wires, Insulation breakdown, wires broken
  Defective coil
  Cracked or dirty distributor cap
  Dirty carburetor
  Vacuum leak at manifold or carburetor base
  Fuel pump pressure Too low - can't supply the carburetor
  Fuel pump pressure Too high - unseats the needle and seat
  Low compression (Also check for blown head gasket)
  Loose or worn distributor (Timing changes)
  Water leaking into cylinders,   Head gasket, exhaust manifold,
           cracked head or valve seat
  Loose or broken engine mounts

Engine Acceleration Is Poor?

  Idle mixture screws Incorrect ignition timing
  Incorrect distributor or amplifier advance curve
  Accelerator pump (Check for stream of raw fuel from
    accelerator pump discharge nozzle, when opening throttle
    with engine shut off)
  Cracked or dirty distributor cap or rotor
  Vacuum leak Intake manifold or carburetor base
  Spark plugs Fouled, burned; wrong heat range; cracked porcelain
  Float adjustment
  Dirty carburetor
  Low compression
 

Engine Runs Poorly At High RPM?

  Crankcase overfilled with oil, Check oil level with boat
    at rest in the water.
  Anti-siphon valve (if equipped) Restricting fuel supply
  Plugged fuel tank vent
  Fuel supply
  Ignition timing
  Low grade of fuel or water in the fuel
  Spark plugs Fouled, burned, cracked porcelain, incorrect heat range
  Spark plug wire, Poor insulation, broken wires
  Distributor cap or rotor Dirty or cracked Coil
  Distributor Excessive play in shaft
  Engine overheating Refer to "Engine Overheats"
  Low compression (Worn valves, rings, cylinders, etc.)
  Restricted exhaust
  Dirty Flame arrestor ( Wrong One?)
  Not enough air flow in engine room ( open Hatch)
  Sterndrive malfunction or seizing

Fuel System Rich?

  Warm engine carburetor percolation, ( Fuel boils out of float
     bowl when shut off and warm. Floods intake manifold.)
  Clogged flame arrestor
  Automatic choke not opening
  Float adjustment
  Float leaks or is saturated with fuel
  Needle and seat leaking
  Carburetor gaskets leaking
  Excessive fuel pump pressure (Unseats needle and seat)
  Cracked or porous carburetor body

Fuel System Lean?

  Empty fuel tank
  Fuel shut-off valve closed (if equipped)
  Vapor lock Engine will not start after warm engine shut down
  Automatic choke Stuck open, wrong adjustment
  Fuel tank vent plugged Engine will start initially. After a
     short time of running, engine will stall and will not
     restart for a period of time. Can verify it is a vent
     problem by running engine with filler cap loose.
     Fill cap will act as a vent.
  Air leak on suction side of fuel system (Sucks air into fuel
     system reducing fuel volume)
  Plugged or pinched fuel line
  Fuel pump Low pump pressure

Carburetor Malfunction?
  Flooding:
            Needle and seat
            Float adjustment,
            Saturated float,
            Gaskets leaking,
            Cracked fuel bowl,
            Fuel percolation,
            Automatic choke,
  Rough idle:
            Idle RPM too low
            Idle mixture screws
            Idle passages dirty
            Throttle valves not closing
            Engine flooding
            Vacuum leak
            Throttle body heat passages plugged
  Hesitation or acceleration flatness:
            Accelerator pump
            Leaking gaskets
            Automatic choke
            Power piston or power valve
            Throttle valves
            Throttle body heat passages plugged
            Main metering jets
            Float adjustment
            Secondary air valve wind-up
  Engine surges:
            Main metering jets
            Leaking gaskets
            Float adjustment
            Saturated float
            Power piston or valve
            Throttle valves
  Low top speed or lack of power:
            Power piston or valve
            Float adjustment
            Main metering jets
            Leaking gaskets
  Poor cold engine operation:
            Idle RPM too low
            Idle mixture screws
            Throttle valves