Overview & Technical Specifications

The 1965 Mercury 9.8 horsepower outboard, designated as the Merc 110, is a twin-cylinder, two-stroke marine engine revered for its impressive power-to-weight ratio and distinct “Phantom Black” styling. Engineered during the golden era of Carl Kiekhaefer’s leadership, this motor remains a favorite among vintage boat enthusiasts and utility boaters alike.

Common Maintenance & Tune-Up Specs

Keeping a vintage Merc 110 running smoothly requires periodic adjustment of the ignition system, fuel system calibration, and gearcase maintenance.

1. Ignition & Electrical System

• Spark Plugs: Champion L86C or NGK B6HS (Modern equivalents). Original specifications often listed Champion L4J.
• Spark Plug Gap: 0.030 inches (0.76 mm).
• Breaker Point Gap: 0.020 inches (0.51 mm). Point condition is critical; ensure contacts are free of pitting, oil, and oxidation.
• Timing: Mechanical advance. Ensure the throttle cam link is synced correctly with the carburetor pick-up point as the magneto plate rotates.

2. Fuel System & Carburetor

• Carburetor Model: Tillotson (typically AJ or KB series).
• Idle Mixture Adjustment (Low Speed): Initial starting point is 1 to 1-1/4 turns open from gently seated. Adjust with the motor warm and running in gear. Turn clockwise to lean, counter-clockwise to richen.
• Main Jet (High Speed): Typically fixed jet on 1965 models, meaning no high-speed needle adjustment is necessary.

3. Lower Unit & Cooling Pump

• Water Pump Impeller Part Number: Quicksilver 47-89981-1 (or modern Sierra equivalent 18-3017). Replacing this impeller every 2-3 seasons is critical to avoid overheating.
• Gearcase Lubricant: High-performance marine SAE 90 gear lube (e.g., Quicksilver Premium Gear Lube).
• Gearcase Capacity: Approximately 3 to 4 oz. Fill from the bottom drain screw until fluid begins to weep out of the top vent hole.

Notable Features & History

The 9.8 HP Merc 110 was first introduced in 1962 and quickly became one of the most successful portable outboard designs in marine history. It remained in production with minor cosmetic and mechanical variations for over two decades. By 1965, the motor had cemented its reputation as a reliable workhorse.

Key Engineering Innovations

• Jet-Prop Exhaust: Unlike many competitor outboards of the mid-1960s that vented exhaust above the cavitation plate, the Merc 110 routed exhaust directly through the propeller hub. This muffled the engine’s noise underwater and improved overall engine breathing and performance.
• Glide-Angle Design: The lower unit and leg feature a swept-back, angled configuration. This slanted design allowed the outboard to easily slip over underwater obstacles, weeds, and logs without hanging up.
• F-N-R Gear Shift: Despite its compact size, the 1965 Merc 110 featured a full Forward-Neutral-Reverse gearshift lever located on the starboard side of the cowl, offering far superior maneuverability compared to smaller “direct drive” or “spin-around” motors.
• Lightweight Portability: Weighing only around 65 pounds, the motor was easily transportable by a single person, making it the perfect match for car-toppers, jon boats, and small fishing vessels of the era.

Today, the 1965 Mercury 9.8 HP remains highly collectible and practical. Thanks to the robust engineering of the Kiekhaefer-era Mercury marine division, parts like points, condensers, carb kits, and water pump impellers are still widely available, allowing these classic black outboards to continue running on waterways around the world.