The 1988 Mercury 25 HP Outboard is a reliable two-stroke marine engine designed for small to medium-sized boats. This manual covers operation, maintenance, troubleshooting, and specifications for the 25 horsepower model featuring electric start, manual tilt, 2-cylinder configuration, and compatibility with various propeller sizes. Below are key sections for safety, features, installation, operation, maintenance, and troubleshooting.
Key components: 2-cylinder two-stroke engine, electric start system, manual tilt mechanism, fuel tank, throttle/shift controls, and propeller assembly.
| Feature | Description |
|---|---|
| Engine Type | 2-cylinder two-stroke outboard |
| Starting System | Electric start with manual backup |
| Tilt System | Manual tilt with locking positions |
| Fuel System | Integrated fuel pump and carburetor |
| Gear Shift | Forward-Neutral-Reverse |
| Propeller | 3-blade aluminum, various pitch options |
| Ignition System | CDI electronic ignition |
| Cooling System | Water-cooled with thermostat |
| Weight | Approximately 105 lbs (48 kg) |
| Shaft Length | 15-inch and 20-inch options |
Proper installation ensures optimal performance and safety.
WARNING! Ensure transom can support engine weight. Use proper mounting hardware and follow torque specifications.
Initial setup and break-in procedure for new engine.
CAUTION! Always operate in well-ventilated area. Follow break-in procedure carefully to ensure engine longevity.
Understanding engine controls and proper operation procedures.
Control Panel: Key switch, choke button, emergency stop switch, tilt release.
Operation: Turn key to ON position; push choke for cold starts; turn to START position. Allow engine to warm up before applying throttle. Use shift lever smoothly between Forward, Neutral, and Reverse positions. Monitor temperature and oil indicators.
Throttle Control: Progressive acceleration; avoid sudden full-throttle applications. Use trim adjustment for optimal boat performance in different water conditions.
Regular maintenance ensures reliable performance and extends engine life.
| Interval | Maintenance Task |
|---|---|
| Each Use | Check fuel system for leaks; inspect propeller |
| 20 Hours/Monthly | Check gearcase oil; inspect spark plugs |
| 100 Hours/Annually | Change gearcase oil; replace water pump impeller |
| 300 Hours/3 Years | Replace fuel lines; inspect carburetor |
| As Needed | Replace anode; grease fittings; check electrical connections |
Note: More frequent maintenance may be required in saltwater or heavy use conditions.
Proper fuel system maintenance is critical for engine performance.
Tip: Use fuel stabilizer if engine will be stored for more than 30 days.
Electrical components and maintenance procedures.
WARNING! Disconnect battery before performing electrical work. Avoid creating sparks near fuel system.
Proper storage procedure to protect engine during off-season.
CAUTION! Store in upright position. Cover to protect from dust and moisture.
EPA Certified: Meets 1988 marine engine emission standards. US Coast Guard: Complies with marine safety requirements. Copyright © 1988 Mercury Marine; trademarks of Brunswick Corporation. For technical support, contact Mercury Marine Customer Service at 1-920-929-5040 or visit www.mercurymarine.com.
| Symptom | Possible Cause | Corrective Action |
|---|---|---|
| Engine won't start | Fuel, spark, or compression issue | Check fuel supply; inspect spark plugs; verify compression |
| Engine runs rough | Carburetor adjustment or fuel quality | Clean carburetor; adjust mixture; use fresh fuel |
| Overheating | Water pump or thermostat failure | Replace water pump impeller; check thermostat |
| Loss of power | Fuel restriction or propeller damage | Check fuel filter; inspect propeller for damage |
| Electrical failure | Battery or charging system | Test battery; check alternator output; inspect connections |
Service: Contact authorized Mercury Marine dealer for major repairs. Technical support: 1-920-929-5040