Mercury 20 HP Rope Start Long Shaft Outboard Motor

The Mercury FourStroke 20 ML EFI is a 4-stroke outboard marine engine designed for small fiberglass, aluminum, or inflatable boats requiring a long shaft, measuring 2.5–5 meters. It features a 20 HP / 14.7 kW and 333 cc 2-cylinder engine. The FourStroke 20 ML EFI, with its 333 cc EFI FourStroke engine, offers economical and reliable power to small and medium-sized boat users.

FourStroke 20 ML EFI Series Features and Technology Advantages

The 2-cylinder design offers balanced power with a compact and lightweight design. EFI injection ensures reliable starting without requiring a manual fuel system.

• 2-Cylinder Engine (333 cc): The 2-cylinder design offers balanced power with a compact and lightweight design
• Long Shaft (508 mm (20")): The propeller operates at an optimal depth for the correct transom height
• EFI Electronic Injection: No primer pump required — automatic fuel system prime before turning the key
• Manual Start: Battery-independent reliable mechanical starting
• Manual Trim: Manually adjust the transom angle — simple and reliable mechanical structure
• 12-Liter Internal Tank: Ready for daily short-distance use; external fuel tank input available

Long Shaft — What Boat Type Is It Suitable For?

The long shaft (508 mm (20")) is suitable for the vast majority of inflatable boats, aluminum boats, and fiberglass boat models. For boats with a transom height of 381 mm, a short shaft model should be preferred.

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
• Backup engine: reliable Mercury service network access

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 after every use is mandatory.

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

Frequently Asked Questions

What boat size does the Mercury FourStroke 20 HP engine fit?

20 HP power can fit 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 advantages 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 oil change every 100 hours or once a season. Impeller checked every two seasons. In saltwater use, freshwater flushing after every use is mandatory. End-of-season fuel system protection is recommended.

Which boat and inflatable boat brands is the FourStroke 20 ML EFI compatible with?

Mercury outboard engines 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 508 mm (20") 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 Engines
• Mercury Marine Products
• Mercury Spare Parts
• Mercury 2.5–30 HP FourStroke
• Mercury 40–60 HP FourStroke
• Outboard Engines
• 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 confirm together if the Mercury FourStroke 20 ML EFI engine is suitable for your boat and the correct shaft choice.