Tractor Screws for Outboards.
AS ” WS. ” remarks in last month’s MOTOR SPORT, pusher type propellers are used on nearly all outboard motors. One American firm of out board manufacturers, however, adopted the tractor screw on their racing models some time ago, and the writer has had considerable experience with thesmotors.
So far as speed is concerned, the use of the tractor instead of the pusher propeller makes little, if any, difference, and the fastest outboards built to-day use pusher propellers.
This may be due to the fact that further experiment is necessary to find the correct design and position for the tractor propeller, but it should be borne in mind that althougn mounting the screw in front of the gear housing allows a. clear run of water to the propeller, it causes a considerable interruption of the flow away from the propeller, which is an important point.
It was the writer’s experience that steering with these motors was decidedly tricky. It was necessary to hold the tiller very firmly, otherwise it would jerk out of one’s hand and slap hard over, with disastrous results. When steering with a wheel (which is the only satisfactory way of controlling a racing outboard), it was necessary to see that the steering cable and connections were exceptionally taut and strong, if an involuntary immersion was to be avoided.
F. H. S. Welwyn, Herts.
