Overview & Technical Specifications

By 1972, the 18 HP Fastwin had benefited from more than a decade of refinement on OMC’s legendary 22-cubic-inch powerhead. It utilized a modern, single-line fuel pump system (eliminating the old, dangerous dual-line pressurized tanks of the 1950s) and featured a full jewel-bearing design for smooth, high-RPM operation.

Common Maintenance & Tune-up Specifications

Keeping a 1972 Fastwin running flawlessly requires attention to its traditional ignition system and water pump. Below are the precise technical specifications needed for a comprehensive tune-up.

Ignition System

This motor utilizes the classic OMC Universal Magneto ignition. It houses two sets of points, two condensers, and two ignition coils directly under the flywheel.

• Spark Plugs: Champion L82C (or Champion UL81C for extended trolling/low-speed use)
• Spark Plug Gap: 0.030 inches (0.76 mm)
• Points Gap: 0.020 inches (0.51 mm) at high lobe of the cam
• Ignition Timing: Set automatically by setting the correct points gap of 0.020″ using a timing fixture or multi-meter.

Carburetor & Fuel System

The Fastwin uses a single-barrel, float-feed carburetor with a low-speed adjustable idle circuit and a fixed high-speed jet.

• Low-Speed Idle Needle Adjustment: Start by gently seating the needle clockwise until it stops. Back it out counter-clockwise 1.5 turns as a baseline. Fine-tune with the engine warm and running in forward gear in the water.
• High-Speed Jet: Fixed (No adjustment needed; check for debris in the brass orifice at the bottom of the float bowl if suffering from high-speed fuel starvation).
• Fuel Filter: Glass/plastic sediment bowl filter located on the side of the powerhead. Clean the mesh screen regularly.

Lower Unit & Water Pump

• Gearcase Lubricant: Standard Marine 80W-90 Gear Oil (OMC Hi-Vis or equivalent)
• Gearcase Oil Capacity: Approx. 9.5 oz (Fill from the bottom drain screw hole until oil begins weeping out of the top level screw hole).
• Impeller Service: Located in the upper gearcase housing. Inspect annually; replace every 2 to 3 seasons. If the motor has sat idle for several years, replace the impeller before attempting to start.
• Propeller Drive: Shear-pin drive system. Always carry spare shear pins (OMC Part #307949 or equivalent) and cotter pins onboard.

Notable Features & History

The Peak of the “OMC Universal Magneto”

The 1972 18 HP Evinrude showcases the absolute refinement of the OMC Universal Magneto system. While solid-state electronic CDI (Capacitor Discharge Ignition) systems began showing up in the mid-1970s, this motor’s points-and-condenser ignition is incredibly robust, highly resistant to moisture, and remarkably easy for DIY mechanics to service with basic hand tools.

50:1 Fuel Mix and Bearings Upgrade

Early iterations of the 22-cubic-inch OMC powerhead in the late 1950s required a heavy 24:1 fuel-to-oil mix because they utilized bushing-style bearings on the wrist pins. By 1972, the Fastwin utilized full needle and roller bearings throughout the internal rotating assembly. This engineering advancement allowed Evinrude to safely specify a lean, modern 50:1 mix ratio, drastically reducing smoke, spark plug fouling, and environmental impact.

Thermostatically Controlled Cooling

Unlike earlier vintage outboards that ran freezing-cold lake water directly through the engine block, the 1972 Fastwin features a built-in thermostat. This allowed the motor to quickly reach and maintain an optimum operating temperature of approximately 140°F (60°C). This feature greatly improved fuel atomization, prevented carbon buildup during long hours of idling/trolling, and extended the service life of the cylinders.

An End of an Era

The 18 HP Fastwin was one of Evinrude’s longest-running and most successful mid-range platforms. 1973 would be the final year for this specific 22-cubic-inch powerhead design, as OMC shifted production to the redesigned 9.9/15 HP and 20/25 HP platforms in 1974. Consequently, the 1972 model is highly prized today as one of the most reliable and fully-matured versions of this classic outboard family.