1988 25 hp Mercury Outboard Manual

The 1988 Mercury 25 hp outboard motor is a reliable two-cylinder marine engine featuring electric start, 12-volt charging system, thermostat cooling, single-lever control, water pump impeller cooling, CD ignition system, and compatibility with various boat types. Below are key sections for safety, specifications, operation, maintenance, troubleshooting, and service procedures.

Features at a Glance

Key components: Two-cylinder engine, electric start system, CD ignition, thermostat-controlled cooling, single-lever control, 12V charging system.

Installation

Proper installation ensures optimal performance and safety.

1. Mounting: Use correct transom height (15" standard); ensure solid mounting surface.
2. Steering: Connect steering cable or tiller handle securely.
3. Electrical: Connect battery cables (red to positive, black to negative).
4. Fuel System: Install fuel line with primer bulb; use Mercury recommended fuel mix.
5. Controls: Connect single-lever control box to engine cables.

WARNING! Engine is heavy; use proper lifting equipment. Ensure all connections are secure before operation.

First-Time Setup

Initial setup procedures for new installation.

1. Fuel mixture: Prepare 50:1 fuel/oil mixture (87 octane gasoline with TC-W3 oil).
2. Priming: Squeeze primer bulb until firm; set choke for cold start.
3. Battery: Connect fully charged 12V battery; check connections.
4. Water test: Run engine in test tank or with water muffs before boat installation.
5. Break-in: Follow break-in procedure for first 10 hours of operation.

CAUTION! Always provide adequate water supply when running engine out of water.

Specifications

• Horsepower: 25 hp at 5000 RPM
• Cylinders: 2 cylinders in-line
• Displacement: 21.9 cubic inches (359 cc)
• Bore x Stroke: 3.00" x 2.32" (76.2mm x 58.9mm)
• Ignition: CD capacitor discharge
• Starting: Electric start (standard)
• Gear Ratio: 12:27 (2.08:1)
• Full Throttle RPM: 5000-5600 RPM
• Fuel/Oil Ratio: 50:1 with TC-W3 oil
• Weight: 105 lbs (electric start model)

Controls and Operation

Control panel features: Key switch, choke, throttle/shift lever, neutral safety switch.

Starting Procedure: Turn key to ON; push in key for choke (cold start); turn to START position. Release key when engine starts.

Single-Lever Control: Forward movement increases throttle; neutral position allows shifting; reverse movement engages reverse gear.

Operation Tips: Allow warm-up at idle; avoid prolonged trolling; monitor water pump discharge.

Fuel System

Fuel system components: Fuel tank, hose with primer bulb, fuel pump, carburetor.

1. Fuel mixture: Always use 50:1 gasoline to TC-W3 certified oil.
2. Primer bulb: Squeeze until firm before starting.
3. Carburetor: Single barrel with fixed jet; adjustable idle mixture.
4. Fuel filter: Replace annually or every 100 hours.

Tip: Use fresh fuel; avoid ethanol blends above 10% when possible.

Maintenance Schedule

Regular maintenance ensures long engine life.

1. After each use: Flush with fresh water; check for water discharge.
2. Every 100 hours: Replace spark plugs; check fuel filter; inspect water pump.
3. Annual: Change gear lube; inspect propeller; check battery.
4. Every 2 years: Replace water pump impeller; inspect thermostat.
5. Every 3 years: Replace fuel lines; check electrical connections.

WARNING! Always disconnect spark plug wires when performing maintenance.

Winter Storage

Proper storage procedures for off-season.

1. Fuel system: Add fuel stabilizer; run engine to circulate treated fuel.
2. Fogging: Spray fogging oil into carburetor while engine runs.
3. Cooling system: Drain water from engine; run antifreeze through system.
4. Battery: Remove and store fully charged in cool, dry location.
5. Storage: Store upright in dry location; cover to protect from elements.

CAUTION! Never store with fuel in carburetor bowl.

Troubleshooting

Reset: Check all safety switches and connections.

Service: Contact authorized Mercury Marine dealer for technical support.