Johnson Evinrude Outboard Motors 1956-1970 1.5-40hp repair manual., Page 10Get this manual
If the power train was to absorb an impact great enough to stop rotation, even for an instant, something would have to give and be damagedIf propeller is subjected to repeated striking of underwater objects, it would eventually slip on its clutch hub under normal loadsIf the propeller would start to slip, new hub and shock absorber would have to be installedPropeller RakeIf propeller blade is examined on cut extending directly through the center of the hub, and if the blade is set vertical to the propeller hub, as shown in the accompanying illustration, the propeller is said to have zero degree (00) rakeAs the blade slants back, the rake increasesStandard propelo lers have rake angle from to 15 higher rake angle generally improves propeller performance in cavitating or ventilating situationOn lighter, faster boats, higher rake often will increase performance by holding the bow of the boat higherProgressive Pitch Progressive pitch is blade design innovation that improves performance when forward and rotational speed is high andor the propeller breaks the surface of the waterProgressive pitch starts low at the leading edge and progressively increases to the trailing edge, as shown in ,the accompanying illustrationThe average pitch over the entire blade is the number assigned to that propellerIn the illustration of the progressive pitch, the average pitch assigned to the propeller would be 21