A Long Way Since The Hand-Crank
Published: Monday, February 3, 2020
By: Professionals of Henry H. Smith Co.
The modern screw propeller was invented by John Patch as a double bladed, fan shaped device. It propelled his boat across the harbor in Yarmouth, Nova Scotia, in the summer of 1833 using a hand-cranked propeller shaft. This inboard propeller shaft configuration continued to be used with the development of engine powered boats, connected to steam engines (replacing paddle-wheels), and eventually internal combustion engines. Modern engines, and even hybrid or electric inboards, continue to use this inboard propeller shaft drive configuration.
With inboard drives, the controls are very simple and limited. Changing the speed and rotation of the propeller moves the boat forward and reverse while a separate rudder system is required for steering. Transmissions provide propeller speed control and may provide optimum shaft angle relative to the engine. The drive trim angle is fixed by the designed configuration and requires a separate trim tab system to compensate. Boat designs and hull shapes are compromised in some ways by the accommodation of the engine/shaft drive systems. Similarly, the propulsion shaft angle and position are controlled by the hull shape and packaging within the hull.
Outboard engines were introduced in the early 1900s and offered a combination of these controls (geared propulsion, steering, and trim) all within a package that did not interfere with the boat’s hull or interior space. The problem with these early outboards was their limited power. Two-stroke designs were used primarily due to their simplicity, light weight, and lower cost; great for smaller boats, but larger boats required these same benefits with much more power.
The need for more horsepower in combination with the benefits of outboard controls led to the development of the sterndrive or I/O (inboard/outboard) designs introduced in the 1960s. With sterndrives, engines could be mounted inside the transom providing more interior room and connecting through a full transom to a drive and lower unit similar to the outboard.
Variations of these drive elements resulted in outstanding alternatives with remarkable performance characteristics. These innovations include pod-drives, Z-drives or azimuth thrusters. These transmit the inboard engine’s power to a propulsion unit similar to an outboard lower unit, but below the boat and able to rotate 360 degrees, providing even better control. Jet drives or pump-jets provide similar functions but, rather than using propellers, the engines power high performance pumps with the output nozzle providing thrust to direct the boat.
Outboard development and innovation has also continued. Outboards today offer four-stroke, clean, quiet, and fuel efficient engines with the horsepower and torque required for much larger boats. Outboards with higher horsepower are now being used on performance boats and cruisers, using multiple engines coordinated electronically to achieve exceptional performance.
The future evolution potential of our marine drives is not clear, but understanding the innovative efforts and sophisticated development results we are currently enjoying, we can be certain that the future will be propelled in a revolutionary direction!
By Professionals of Henry H. Smith Co., www.henrysmith.com
Founded in Detroit by Henry H. and William H. Smith, the company continues to employ 3rd and 4th generation members of the family, carrying on a legacy established in 1900 - to be your Marine Drive Specialists.
This article first appeared in the Winter Issue (Jan/Feb) 2020 of Great Lakes Scuttlebutt magazine.
tags: Engines, Propellers
