1949 Mercury 5 HP Super 5 Mark 5 Outboard Specs & Part Numbers
Introduction
The late 1940s marked a golden era for recreational boating, and Kiekhaefer Mercury was at the forefront of this revolution. Introduced in 1949, the Mercury 5 HP “Super 5” (Model KF-5)—which laid the groundwork for the legendary Mark 5 designation—offered unprecedented performance, lightweight design, and engineering innovations that left competitors scrambling. This technical guide provides a deep dive into the specifications, maintenance procedures, and historical context of this classic alternate-firing twin outboard motor.
Overview & Specifications
The 1949 Mercury KF-5 “Super 5” was engineered to be a lightweight, high-performance utility motor. Unlike many of its contemporaries, which relied on heavy cast-iron components and plain bushings, the KF-5 featured extensive use of aluminum alloys and anti-friction bearings.
| Parameter | Specification |
|---|---|
| Manufacturer | Kiekhaefer Mercury (Fond du Lac, Wisconsin) |
| Model / Series | KF-5 “Super 5” (Precursor to the Mark 5 series) |
| Production Year | 1949 (Production ran 1949–1951) |
| Horsepower Rating | 5.0 HP @ 4,200 RPM |
| Engine Type | Alternate-firing two-stroke twin (2-cylinder) |
| Displacement | 7.2 cubic inches (118 cc) |
| Bore x Stroke | 1.750 in. x 1.500 in. (44.45 mm x 38.1 mm) |
| Weight | Approximately 40 lbs (18 kg) |
| Fuel/Oil Ratio | 16:1 (1/2 pint of TC-W3 or SAE 30 outboard oil per 1 gallon of regular gasoline) |
| Starting System | Manual rewind starter (automatic pullback) |
Common Maintenance & Tune-up Specs
Keeping a vintage 1949 Mercury running smoothly requires attention to ignition systems, carburetion, and cooling. Below are the critical tune-up specifications required for maintaining or restoring this motor.
Ignition System Specs
- Magneto Type: Bendix-Scintilla or early Kiekhaefer magneto.
- Spark Plug Type: Champion J8C (or equivalent modern Champion 841). For colder running, J6C may be used.
- Spark Plug Gap: 0.025 inches (0.64 mm).
- Breaker Point Gap: 0.020 inches (0.51 mm).
- Condenser Capacity: 0.15 to 0.20 microfarads.
Fuel & Carburetion Specs
- Carburetor Model: Tillotson AJ3A or AJ4A side-draft slide-valve carburetor.
- High-Speed Needle Adjustment (Bottom/Main Jet): Start at 1 to 1-1/4 turns open from gently seated. Adjust on the water under load.
- Low-Speed/Idle Needle Adjustment (Top Jet): Start at 3/4 to 1 turn open from gently seated.
- Fuel Delivery: Gravity-fed from the integrated overhead tank. Ensure the fuel petcock screen is free of debris.
Cooling & Gearcase Specs
- Impeller / Water Pump: Located inside the lower unit gear housing. The KF-5 utilizes a flexible rubber impeller driven by the driveshaft. If dry-rotted or stiff, replace immediately to prevent powerhead overheating.
- Lower Unit Lubricant: Originally specified for Lubriplate 105 or “grease” style lube. For modern operation, use a high-quality, non-corrosive, semi-fluid outboard gear grease (such as Lubriplate 105 or John Deere Corn Head Grease) rather than heavy 90W gear oil, as the seals on these vintage units were not designed to hold thin fluids.
Notable Features & History
Carl Kiekhaefer’s “Full Jeweled Power”
One of the most significant marketing and engineering triumphs of the 1949 Mercury Super 5 was the introduction of “Full Jeweled Power”. This term referred to Kiekhaefer’s use of anti-friction ball and roller bearings throughout the entire engine. While competitors like Evinrude and Johnson were still using cheaper, high-wear bronze bushings on the crankshaft and connecting rods, Mercury used precision roller bearings. This design minimized friction, reduced heat, allowed for higher RPM potential, and significantly extended the lifespan of the motor.
The Rotary Valve & Reed Intake
Unlike standard piston-port engines of the era, the KF-5 utilized an internal reed-valve crankcase induction system. This allowed for superior fuel-air mixture delivery across a broad RPM range, yielding incredibly smooth idling capabilities and snappy throttle response. It made the Super 5 highly sought after by both fishermen looking to troll at ultra-low speeds and racers looking for a lightweight power unit.
Styling and Legacy
The 1949 Super 5 featured a distinctive “green tank” livery with polished aluminum trim, embodying the classic post-WWII streamline aesthetic. The success of the KF-5 solidifed Mercury’s reputation as a performance brand. In 1953, Kiekhaefer transitioned this 5 HP platform into the official Mark 5 designation, carrying over the same basic block geometry and internal engineering that had proven so reliable in the 1949 Super 5.
Collector & Restoration Tips
If you are restoring a 1949 KF-5 today, pay close attention to the following:
- Coils: The original Scintilla magneto coils are notorious for cracking over time due to age and moisture. Modern replacement coils can be retrofitted under the flywheel.
- Cracked Fuel Lines: The copper and brass fuel lines can fatigue. Ensure the compression fittings are clean and leak-free to avoid fire hazards under the cowling.
- Transom Brackets: Ensure the cast-aluminum transom clamps are free of hairline cracks, a common point of failure if the motor was subjected to rough trailering over the years.