Yamaha 5bs 661 |verified| Jun 2026

While the 5BS is built to last, engines from this era require specific attention to remain operational:

The is a classic air-cooled, single-cylinder two-stroke outboard motor produced between 1973 and 1986. Known for its simplicity and rugged reliability, this 5-horsepower engine is a favorite for light-duty fishing and leisure boating. Because it is air-cooled, it lacks a water pump impeller, significantly reducing common maintenance headaches associated with traditional water-cooled outboards. Key Specifications Engine Type : Two-stroke, single-cylinder, air-cooled. Displacement : 103 cc. Output : 5 horsepower at 4500 RPM. Weight : Approximately 19 kg (approx. 42 lbs).

Here’s everything you need to know about the 5BS-661 identifier. yamaha 5bs 661

Single carburetor with a pre-mixing ratio of 1:50 Ignition: Breaker points (contact points) Design and Practicality

The is a testament to Japanese engineering from the golden age of two-strokes. While it is just a forged steel bar with a hole in each end, it represents the heartbeat of the RD400—a motorcycle that refused to die quietly. While the 5BS is built to last, engines

Before ordering a 5BS 661 part, verify your crankshaft's "big end pin" diameter and "small end" bushing ID. Yamaha produced mid-year revisions. A 1976 RD400 rod differs slightly from a 1979 RD400F rod even if the 5BS code remains.

: Compatible with some Mariner brand parts from the same era. Maintenance Essentials Weight : Approximately 19 kg (approx

The Yamaha 5BS-661 is not just a model number; it represents a specific mechanical package. While variations exist, the standard specifications for this 50hp short shaft engine are as follows:

The heart of the 5BS-661 is its inline 3-cylinder configuration. Unlike V4 or V6 engines, the inline-3 is renowned for being compact and lightweight. This design reduces the overall mass hanging off the transom, which improves the boat's balance and fuel efficiency. Furthermore, the three-cylinder 2-stroke cycle provides a smooth power delivery with a distinctive throaty sound that vintage enthusiasts love. It offers significantly more torque than a twin-cylinder 40hp engine, making the jump to the 5BS-661 a noticeable upgrade in performance.

To keep this vintage motor running smoothly, follow these routine checks:

for those who prioritize weight and simplicity over quiet operation. It is ideal for short trips or as an emergency backup where you need an engine that will start after sitting for long periods. repair manual to help with a specific maintenance task on this motor? Yamaha 5 BS air-cooled - YBW Forum