1986 Evinrude 20 HP Outboard Specs & Part Numbers
Introduction
The 1986 Evinrude 20 HP is a legendary two-stroke outboard motor engineered by the Outboard Marine Corporation (OMC). Renowned for its excellent power-to-weight ratio, mechanical simplicity, and rugged durability, this twin-cylinder motor remains a favorite among vintage boat enthusiasts, anglers, and duck hunters. Whether you are restoring a classic hull or keeping a reliable workhorse running, this technical guide provides the essential specifications, maintenance parameters, and historical context for the 1986 model year.
Overview & Specifications
In 1986, Evinrude utilized its proven 31.8 cubic inch (521 cc) twin-cylinder powerhead for the 20 HP model. This block was shared with the 25 HP sister model, meaning the 20 HP operates under low stress, contributing to its exceptional operational lifespan.
| Specification | Details |
|---|---|
| Propshaft Horsepower | 20 HP (14.9 kW) @ 5000 RPM |
| Engine Type | 2-Cylinder, 2-Stroke, Inline Crossflow |
| Displacement | 31.8 cu. in. (521 cc) |
| Bore & Stroke | 2.500″ x 2.438″ (63.5 mm x 61.9 mm) |
| Fuel/Oil Ratio | 50:1 (Regular unleaded 87 octane to TC-W3 Marine Oil) |
| Starting System | Manual (Rope Start) or Electric (Optional models) |
| Weight | Approx. 115 lbs (52 kg) for short shaft (15″) manual model |
| Gear Ratio | 12:21 (0.57) |
Common Maintenance & Tune-up Specs
To keep the 1986 Evinrude 20 HP running at peak performance, regular seasonal maintenance is required. Because this model features OMC’s electronic ignition system, maintenance is highly streamlined compared to older point-and-condenser outboards.
Ignition & Electrical
- Spark Plug Type: Champion QL77JC4 (or L77JC4)
- Spark Plug Gap: 0.030 inches (0.76 mm)
- Points Gap: Not Applicable (N/A). This model utilizes a solid-state Capacitor Discharge Ignition (CDI) system, eliminating mechanical breaker points.
- Ignition Timing: Factory-set, controlled via the mechanical linkage advance. Adjustments should only be made using a timing light following the OEM service manual instructions.
Fuel System
- Carburetor Type: Single-throat float-feed carburetion with manual choke (or electric primer solenoid on electric-start packages).
- High-Speed Jet: Fixed orifice (No adjustment needed; must be physically replaced if running at high altitudes).
- Low-Speed (Idle) Mixture Needle: Adjustable. Initial setting is typically 1.5 turns out from gently seated.
Gearcase & Cooling
- Gearcase Lubricant: OMC Hi-Vis Marine Gearcase Lube (or high-quality 80W-90 marine gear oil).
- Gearcase Capacity: Approximately 9.0 fl. oz. (266 ml). Always fill from the bottom drain hole until fluid exits the top vent hole to prevent air pockets.
- Impeller Information: Part Number: OMC 395289 (Sierra 18-3051). The water pump impeller should be inspected annually and replaced every 2 to 3 seasons, or immediately if water flow from the overboard indicator (tell-tale) becomes weak or intermittent.
Notable Features & History
The OMC 521cc Platform
The mid-1980s marked a highly refined era for OMC outboards. The 1986 Evinrude 20 HP belongs to the legendary 521cc engine family. This powerhead design was so reliable and efficient that it remained in production with minor variations for over two decades. By sharing the same physical displacement as the 25 HP variant, the 20 HP operates under lower internal stress, making it practically bulletproof when properly maintained.
Advanced CDI Ignition
By 1986, the transition away from troublesome mechanical points was fully complete. This motor features a modern CDI electronic ignition power pack. This system produces a hot, consistent spark even at low cranking speeds, resulting in incredibly easy first-pull starts and smooth trolling performance without spark plug fouling.
Thru-Hub Exhaust & Lower Unit Aerodynamics
Unlike older outboards that discharged exhaust gases above the cavitation plate, the 1986 Evinrude 20 HP routes exhaust directly through the propeller hub. This design serves two purposes: it significantly reduces engine noise and vibrations, and it creates a vacuum that pulls exhaust gases away from the boat, resulting in cleaner operation and slightly improved top-end performance.
Legacy & Availability of Parts
Today, the 1986 Evinrude 20 HP is highly sought-after on the used market. Because OMC manufactured hundreds of thousands of these 521cc blocks across both the Evinrude and Johnson brands, OEM and aftermarket parts (such as carb kits, impellers, coils, and seal kits) remain widely available and highly affordable. Its lightweight design makes it the maximum allowable horsepower for many small utility boats, dinghies, and vintage aluminum Jon boats.