1957 Evinrude 18 HP Fastwin Outboard Specs & Part Numbers
1957 Evinrude 18 HP Fastwin
Comprehensive Technical & Restoration Guide
Overview & Specifications
The 1957 Evinrude Fastwin 18 horsepower outboard motor (Models 15020 and 15021) represents the pinnacle of mid-century marine engineering. Positioned as a highly versatile mid-range motor, the Fastwin was incredibly popular for family runabouts, fishing boats, and utility crafts. Known for its robust build quality, smooth idling, and distinctive “Holiday Blue” and gold livery, it remains a highly sought-after model for vintage outboard restorers today.
| Parameter | Specification |
|---|---|
| Power Output | 18 Horsepower @ 4500 RPM |
| Configuration | 2-Cylinder, Two-Stroke, Inline |
| Displacement | 22.0 cubic inches (360.5 cc) |
| Bore x Stroke | 2.500″ x 2.250″ (63.5 mm x 57.15 mm) |
| Fuel System | Dual-line Pressurized Fuel Tank (Cruis-a-Day) |
| Fuel-to-Oil Ratio | 24:1 (1 Quart TC-W3 oil to 6 Gallons of regular 87/91 octane gasoline) |
| Weight | Approx. 79 lbs (Manual start), 87 lbs (Electric start model) |
| Transom Height | 15-inch (Standard Shaft) / 20-inch (Long Shaft) |
Crucial Operating Note: Because this motor utilizes bronze sleeve bearings rather than modern needle bearings on the connecting rods and mains, do not run a 50:1 fuel mixture. A 24:1 mixture is absolutely critical to prevent catastrophic engine failure.
Common Maintenance & Tune-up Specs
To keep the 1957 Fastwin running reliably, periodic maintenance of the OMC Universal Magneto ignition system and fuel system is required. Below are the key tuning parameters and specifications.
Ignition & Electrical System
- Spark Plugs: Champion J4C (historically J4J) or Champion J6C (for slightly warmer operation if idling for long periods).
- Spark Plug Gap: 0.030 inches (0.76 mm).
- Breaker Point Gap: 0.020 inches (0.51 mm). Ensure contacts are clean of any oil or oxidation.
- Condenser Capacity: 0.18 to 0.22 microfarads (mfd).
- Coil Resistance Values: Primary winding should read approximately 1.0 to 1.5 ohms; Secondary winding should read between 5,000 and 8,000 ohms.
Carburetor Settings
The 1957 Fastwin uses a Tillotson or OMC dual-jet carburetor. Use these baseline settings for rebuilding and tuning:
- High-Speed Needle (Bottom Dial): Start at 1 full turn open from gently seated. Adjust on the water under load for maximum RPM and smooth transition.
- Slow-Speed Needle (Top Dial): Start at 1.5 turns open from gently seated. Adjust while idling in forward gear until a smooth, steady idle is achieved.
Water Pump & Lower Unit
- Impeller Replacement: Part number 375638 (or modern equivalent Sierra 18-3002). It is highly recommended to change the impeller every 2-3 seasons. Accessing it requires splitting the gearcase at the lower midsection seam and disconnecting the shift rod connector.
- Gearcase Lubricant: Standard OMC/Evirude Premium Blend or quality marine 80W-90 weight outboard gear lube. Fill from the bottom drain hole until it seeps out of the top level vent hole.
Notable Features & History
The Pressurized Fuel System Challenge
Like most OMC outboards of the mid-to-late 1950s, the 1957 18 HP Fastwin does not have a mechanical fuel pump on the powerhead. Instead, it relies on a pressurized two-line fuel tank system (often referred to as the “Cruis-a-Day” tank). One line sends air pressure from the crankcase down into the fuel tank to pressurize it; the second line delivers fuel under pressure back up to the carburetor.
Restoration Tip: Operating these systems requires ensuring the fuel tank’s rubber lid gaskets and connector seals are completely airtight. Many modern restorers convert these engines to a single-line vacuum fuel pump system using a Mikuni or later-model OMC fuel pump, pulse-driven from one of the crankcase bypass covers.
“Whispering Power” Cushion Mounting
The 1957 model year showcased Evinrude’s commitment to quietness and operator comfort. The Fastwin featured an advanced rubber suspension cradle that isolated the powerhead and midsection from the transom brackets. Along with sound-deadening seals inside the fiber-glass/aluminum composite cowl and an underwater exhaust outlet, this design substantially reduced noise and vibration transferred to the boat hull compared to competitors of the era.
Historical Legacy
The 18 HP Fastwin bridged the gap between smaller trolling motors and heavy-duty cruisers. This specific model year was the sweet spot of OMC durability, utilizing heavy castings, robust components, and the legendary OMC Universal Magneto, which remained fundamentally unchanged for decades due to its sheer reliability. For vintage enthusiasts, the 1957 model is highly prized for its beautiful art-deco styling, ease of repair, and the nostalgic sound of its steady, deep two-stroke idle.