Mercury 3.5 HP Rope-Start Short Shaft Outboard Motor

The Mercury FourStroke 3.5 M is a 4-stroke outboard marine engine designed for small fiberglass, aluminum, or inflatable boats, 2.5–5 meters in length, requiring a short shaft, with 3.5 HP / 2.6 kW and an 85 cc 1-cylinder engine. The FourStroke 3.5 M, with its 85 cc EFI FourStroke engine, offers economical and reliable power to small and medium-sized boat users.

FourStroke 3.5 M Series Features and Technology Advantages

The 2-cylinder design provides balanced power with a compact and lightweight design. EFI injection ensures reliable starting without the need for a manual fuel system.

• 1-Cylinder Engine (85 cc): 2-cylinder design offers balanced power with a compact and lightweight build
• Short Shaft (381 mm (15")): Propeller operates at optimum depth for correct transom height
• EFI Electronic Injection: No primer pump needed — fuel system automatically primes before key turn
• Manual Start: Battery-independent reliable mechanical starting
• Manual Trim: Manually adjust transom angle — simple and reliable mechanical structure
• 1-Liter Internal Tank: Compact and no external tank required — sufficient for short-distance use

Short Shaft — Which Boat Type is it Suitable For?

The short shaft (381 mm (15")) is suitable for the transom height of standard inflatable boats, small fiberglass, and aluminum boats. It should not be confused with the long shaft model.

Technical Specifications

Who is This Engine For?

• 2.5–5 meter small and medium-sized boats: economical EFI power
• Fishing and coastal use: quiet 4-stroke operation
• Inflatable boats and RIBs: lightweight engine and balanced thrust
• Auxiliary engine: access to reliable Mercury service network

Maintenance and Longevity

4-stroke Mercury engines operate trouble-free for many years with regular oil changes and end-of-season maintenance protocols. The impeller of the water-cooled system should be checked every 100 hours or every two seasons. In saltwater use, freshwater flushing is mandatory after each use.

Related maintenance categories: Maintenance Kit | Engine Oil | Impeller | Mercury Spare Parts

Frequently Asked Questions

Which boat size is the Mercury FourStroke 3.5 HP engine suitable for?

3.5 HP power can suit different sizes depending on boat weight and type. General rule: 15–20 kg boat weight per HP. Always check the maximum engine power recommended by the boat manufacturer.

What advantage does the EFI system offer over a carbureted engine?

EFI (Electronic Fuel Injection) does not require a primer pump or choke adjustment. It provides reliable starting in cold weather and at high altitudes, consistent power output, and lower fuel consumption compared to carbureted alternatives.

What are the maintenance intervals for Mercury FourStroke?

Oil change at the first 20 hours, then every 100 hours or once per season. Impeller check every two seasons. Freshwater flush is mandatory after each use in saltwater. End-of-season fuel system protection is recommended.

Which boat and brand models are compatible with the FourStroke 3.5 M?

Mercury outboard motors are compatible with many fiberglass, aluminum, and inflatable boat models thanks to their universal transom clamp or transom mounting system. The only criteria are your boat's 381 mm (15") transom height and the maximum engine power approved by the manufacturer. You can get compatibility confirmation from Clever Marin by sharing your boat model.

Related Products and Categories

• Mercury Outboard Motors
• Mercury Marine Products
• Mercury Spare Parts
• Mercury 2.5–30 HP FourStroke
• Mercury 40–60 HP FourStroke
• Outboard Motors
• Boat Engines
• Maintenance Kit
• Impeller
• Anode

Is This the Right Configuration for Your Boat?

Share your boat model, transom height, and intended use — let's verify together if the Mercury FourStroke 3.5 M engine is suitable for your boat and ensure the correct shaft selection.