OMC Stern Drives And Motors 1964-1986 Repair Manual., Page 10Get this manual
PROPELLERS conditionIf any of the blades become bent or nicked, this condition will set up vibrations in the drive unit and the motorIf the vibration becomes very serious will loss of power, efficiency, and boat performanceIf the vibration is allowed continue over period of can have damaging effect on many of the operating partsVibration in boats can never completely eliminated, but can reduced by keeping all parts in good working condition and through proper maintenance and lubricationVibration can also reduced in some cases by increasing the number of bladesFor this reason, many racers use two-blade props and luxury cruisers have four- and five-blade props installed
How much impact the propeller is able withstand before causing the clutch hub slip is calculated be more than the needed propel the boat, but less than the amount could damage any part of the power trainUnder normal propulsion loads of moving the boat through the water, the hub will not slipHowever, will slip if the propeller strikes an object with force would be great enough stop any part of the power train If the power train was absorb an impact great enough stop rotation, even for an instant, something would have give and be damagedIf propeller is subjected repeated striking of underwater objects, would eventually slip on clutch hub under normal loadsIf the propeller would slip, new hub and shock absorber would have tobe installed