Mariner 25 Marathon problems
| Engine Model: Mariner Mercury Marathon 25 Hp |
| Engine Type: 2-stroke 2-cylinder gasoline outboard engine |
| Total Displacement: 24.4 cu.in (400 cc) |
| Rated Engine Power: 25 Hp (18.7 kW) at 6000 rpm |
| Fuel System: Float type carburetor |
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| Engine will not start or starts up hard |
Gas tank is empty - Add gasoline.
Improper fuel grade - Use quality gasoline.
Dirt and debris in fuel system - Remove debris and dirt.
Defective spark plug wire connection - Inspect spark plug wiring connection, change or repair.
Defective spark plug - Change spark plug as required.
Fuel filter is clogged - Replace or clean fuel filter.
Incorrect carburetor adjustment - Adjust carburetor idle mixture screw.
Fuel lines are clogged - Fuel lines need to be cleaned.
Closed or restricted fuel tank air vent - Open or clean air vent.
Lack of fuel pump pressure - Replace or repair fuel pump.
Reed valve is worn or damaged - Replace reed valve as required.
| Engine starts and then stalls |
Defective spark plug - Replace spark plug.
Faulty or dirty carburetor - Clean or change carburetor.
Ignition coil is faulty - Ignition coil should be replaced.
Closed or clogged fuel tank air vent - Open or service air vent.
Fuel pump pressure is low - Install new pump or repair it.
Defective ignition system - Check ignition and replace faulty components.
Fuel pump is damaged or dirty - Test fuel pump and change if necessary.
Carburetor components worn out - Repair or replace parts.
Dirt in the fuel lines - Fuel lines need to be cleaned.
Fuel tank air vent restricted or closed - Fuel tank air vent need to be opened or cleaned.
Clogged fuel filter - Replace fuel filter.
Worn gaskets - Change gaskets.
Engine overloaded - Load reducing is recommended.
Too lean carburetor mixture - Make the correct settings.
Ignition timing is improper - Adjust ignition timing as required.
Faulty thermostat - Replace thermostat.
Water pump is defective - Replace water pump.
Propeller pitch or diameter incorrect - Check the propeller size.
Propeller bent or damaged - Replace propeller.
Outboard engine is positioned too low or too high - Mount the motor as required.
| Engine knocking sound or abnormal noise |
Stale fuel - Use proper gasoline.
Engine overloaded - Reduce the load.
Incorrectly adjusted low idle speed - Correct idle settings.
Fuel pump is defective or dirty - Service or change fuel pump.
Worn crankshaft or main bearings - Worn parts replacement required.
Piston rings or cylinder bore are damaged - Replace defective parts.
| Engine power is insufficient |
Carburetor is clogged or improperly adjusted - Carburetor needs to be adjusted correctly or cleaned.
Dirty or defective fuel pump - Service or replace fuel pump.
Ignition system is defective - Inspect ignition system and change failed components.
Gaskets are damaged - Replace gaskets.
Powerhead components are faulty - Replace defective components.
Propeller pitch or diameter incorrect - Check the propeller size.
Damaged or improper size of propeller - Replace propeller.
Incorrect outboard motor mounting height - Adjust the engine to correct transom height.
Incorrect trim angle - Make the correct trim angle adjustment.
| Engine uses too much fuel |
Carburetor main jet adjustment is improper - Adjust the carburetor main jet correctly.
Faulty or loose spark plug - Change or re-tighten spark plug.
Piston, sleeve, or rings are damaged - Replace defective parts.
| Excessive engine vibration |
Damaged or improper size of propeller - Replace propeller.
Propeller shaft damaged - Propeller shaft needs to be replaced.
Weeds in the propeller - Clean the propeller.
Motor mounting bolt is loose - Tighten the bolt as required.
Steering pivot is loose or damaged Tighten correctly or replace.
Battery voltage is low - Charge the battery.
Battery runs out quickly - Service battery or change it.
Bad terminals or disconnected battery cables - Connect wiring correctly or install new terminals.
Starter motor is faulty - Starter should be replaced.
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| Outboard Engines Technical Specifications |
| Small Engines Technical Specifications |
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| Industrial Engines Technical Specifications |
