Mercury 25 Bigfoot Troubleshooting
| Engine Model: Mercury Bigfoot 25 |
| Engine Type: 4-stroke 2 or 3 cylinder gasoline outboard engine |
| Total Displacement: 30.4 cu.in (498 cc) or 32.1 cu.in (526 cc) |
| Rated Engine Power: 25 Hp (18.7 kW) at 6000 rpm |
| Fuel System: Carburetor or electronic fuel injection (EFI) |
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| Engine hard to start or doesn't start |
Fuel tank is empty - Fill gasoline up.
Low-quality gasoline - Use quality fuel.
Fuel system clogged - Repair or replace.
Faulty spark plug wire connection - Check the spark plug wire connection, repair or replace.
Spark plug is damaged - Spark plug need to be replaced.
Fuel filter is clogged - Install new filter.
Vapor separator needle valve is damaged or worn - Change vapor separator needle valve.
Fuel lines are dirty - Clean fuel system lines.
Closed or clogged fuel tank air vent - Open or service air vent.
Fuel feed pump failure - Change or rebuild fuel feed pump.
Choke cable is not adjusted properly or worn - Change cable or adjust correctly.
Improper valve clearance - Adjust valve clearance.
Incorrect valve timing - Set the valve timing correctly.
Fuel pressure is low - Inspect low pressure fuel pump or inspect fuel system for leaks.
Clogged or worn fuel injector - Replace or clean if necessary.
Fuel regulator is faulty - Replace fuel regulator.
Electronic control modul is not operating - Install new ECM.
| Engine starts but immediately shuts off |
Faulty spark plug - Install new spark plug.
Vapor separator needle valve is bend or wear - Replace needle valve.
Defective ignition coil - Install a new ignition coil.
Fuel tank air vent restricted or closed - Fuel tank air vent need to be opened or cleaned.
Fuel pump malfunction - Install new pump or repair it.
Damaged choke system - Change choke system components as required.
Excessive valve clearance - Need to adjust valve clearance.
Improper valve timing - Adjust valve timing as required.
Valve springs are weak or broken - Install new valve springs.
Valves are stuck - Valves need to be cleaned.
Poor compression - Inspect and replace defective parts.
Fuel filter is dirty - Install new filter.
Fuel injector is faulty or clogged - Clean or replace if necessary.
Engine oil level is low - Check and refill engine oil.
Faulty oil pump - Install new oil pump.
Water intake screen is dirty - Need to wash or clean.
Damaged thermostat - Change thermostat.
Damaged water pump - Replace water pump.
Defective ignition system - Check ignition and replace faulty components.
Fuel pump is damaged or dirty - Test fuel pump and change if necessary.
Worn or defective vapor separator needle valve - Change vapor separator needle valve.
Dirty fuel lines - Service fuel lines.
Closed or clogged fuel tank air vent - Open or service air vent.
Fuel filter is dirty - Fuel filter needs changing.
Intake manifold air leaks - Install new gasket.
Water intake is blocked - Wash or clean as required.
Throttle valve and throttle link are defective or worn - Change faulty components.
Fuel injector is faulty or clogged - Clean or install new injector.
Engine is under excessive load - Reduce engine load.
Clogged fuel pump or fuel injector - Replace or clean as required.
Wrong ignition timing - Ignition timing needs to be adjusted correctly.
Damaged thermostat - Replace thermostat.
Water pump failure - Change water pump.
Incorrect propeller selection - Check the propeller size.
Damaged or improper size of propeller - Have propeller repaired or replaced.
Outboard motor is mounted too high or too low - Position the engine correctly.
Engine oil level low - Need to add engine oil.
Oil pump malfunction - Install new oil pump.
Dirty water intake screen - Wash or clean as required.
Valve setting is wrong - Set the valves correctly.
Low octane gasoline - Use correct fuel.
Engine is running overloaded - Load reducing required.
Incorrectly adjusted low idle speed - Correct idle adjustment.
Dirty or damaged fuel pump - Service or change fuel pump.
Main bearings or crankshaft failure - Worn parts replacement required.
Worn piston rings or cylinder bore - Replace defective parts.
Restricted fuel lines - Service fuel lines.
Defective fuel injector - Check fuel injector and replace if necessary.
Fuel pump is damaged or dirty - Clean or install new fuel pump.
Ignition system is defective - Check ignition and replace faulty components.
Worn cylinder head gasket - Install new cylinder head gasket.
Worn powerhead components - Change defective components.
Valves are stuck or burned - Clean or change valves.
Incorrect propeller selection - Check the propeller size.
Damaged or bent propeller - Have propeller repaired or replaced.
Outboard engine mounting height improperly - Adjust the outboard motor height correctly.
Improper trim angle - Make the correct trim angle adjustment.
| Engine uses too much fuel |
Fuel injector is faulty or clogged - Clean or replace if necessary.
Defective or loose spark plug - Spark plug need to be replaced or tightened.
Rings, sleeve, or piston are damaged - Change faulty parts.
ECU failure - Replace ECU.
| Motor vibrates excessively |
Damaged or improper size of propeller - Replace propeller.
Propeller shaft malfunction - Have propeller shaft replaced.
Weeds clogs the propeller - Clean the propeller.
Engine mounting bolt is not tightened - Tighten the bolt as required.
Damaged or loose steering pivot Tighten correctly or replace.
Low battery power - Battery is drained, recharge it.
Battery drains quickly - Battery needs service or replacement.
Disconnected wires or corroded battery terminals - Check cables and clean or change terminals.
Starter motor failing - Repair or install a new starter.
| Trim motor runs but trim system does not move up or down |
Oil level low - Fill up oil.
Pump assembly faulty - Check pump and change if required.
Leakage of manual release valve - Valve need to be closed or changed.
Faulty pump driveshaft or motor - Change defective component.
| Trim cannot be fully up or down |
Pump assembly is faulty - Replace pump.
Tilt ram piston ball is not positioned correctly - Clean or repair.
Tilt ram piston O-ring damaged - Install new O-ring.
Not enough oil - Checking oil level and add if necessary.
Lower check valve is not properly secured in port side trim ram - Secure valve properly.
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