1991 Mercury MerCruiser 5.0 L 305 V8 Boat Engine

FOR SALE 1991 Mercury MerCruiser 5.0 L 305 V8 Boat Engine 300 Hrs FRESH WATER. This engine excellent condition, low HOURS and great runs.

The 1991 Mercury MerCruiser 5.0L (305 CID) is a marinized General Motors small-block V8. It features a 220 HP propshaft rating, a 4.00″ bore, and a 3.48″ stroke. It is commonly paired with an Alpha One or Bravo sterndrive.

General Specifications

• Horsepower : 220 HP @ 4800 RPM
• Displacement : 305 cubic inches (5.0 Liters)
• Cylinders : V8
• Operating Range (WOT) : 4,400 – 4,800 RPM
• Idle Speed : ~650 RPM in Neutral

Engine Block & Internals

• Bore x Stroke : 3.737 in X 3.48 in
• Compression Ratio : 9.3:1 (typically)
• Valvetrain : Overhead valve (OHV), Pushrod, Hydraulic flat tappet camshaft
• Firing Order : 1-8-4-3-6-5-7-2

Fuel & Ignition

• Carburetion : Standard 2-barrel (Mercarb/Rochester) or 4-barrel, depending on the specific model variation
• Ignition Timing : Standard base timing is typically 8Before Top Dead Center (BTDC)
• Spark Plug : NGK BPR5ES
• Fuel Requirement : 87 Octane minimum

Fluids & Capacities

• Engine Oil : 5 US Quarts (4.7 L) with filter
• Oil Specification : 20W-40 or 25W-40 NMMA FC-W certified marine oil
• Cooling System : Thermostatically controlled raw-water cooling (approx. 143°F thermostat)