An investigation was carried out to develop a unit of power transmission system for facilitating starting up of watering machines. This unit is used to transmit power after starting the engine and then loading power to other attached member. Three parameters included shaft speed (350, 600, 850 and 1200 rev./min), contact area (100, 150 and 200 cm²) and contacting material (rubber, linen or coarse surface) were tested. The percentage of slip, efficiency of mechanical transferring (contacting efficiency), fuel consumption, power and energy requirements were measured. Total cost was estimated according to the recent prices. The results showed that increasing shaft speed to 1200 rev/min with 200 cm² linen contacting material resulted in increasing contacting efficiency 99.95 % and fuel consumption 2.3 l/h and power and energy requirements of 6.35 kW and 0.42 kW.m³/h, respectively, while decreasing slip percentage to 0.05%. Total costs of fabricating and installing the developed unit were assumed according to the recent market price and were found to be 500 LE. Generally, it is advisable to produce the developed unit in a large scale and install in all watering machines to facilitate and lessen the performance hazards.