What are the correct fitting tolerances for a propeller shaft coupler?
The propeller shaft coupler should fit on the propeller shaft with a fairly tight SLIP fit… so the coupler internal diameter should be .0005″ to .001″ larger than the shaft diameter with all parts at room temperature (ie. 20 C). It should be possible to push on and remove the coupler by hand (heating the coupler by pouring a big pot of boiling water over it may help it slip off the shaft easier when removing it, but it should go on by hand when all the parts are clean and new). The coupler is actually held tight to the shaft when the 2 large set screws (usually 3/8″ NC threaded square-headed bolts on opposite sides to the square keystock in the shaft/coupler) are tightened… and they should be tightened into “dimples” cut into the shaft about 1/16″ with a drill to ensure the shaft cannot back out of the coupler when the transmission is in reverse and the propeller is trying to pull the shaft right out of the boat. Installing the coupler and set screws on the shaft with “Never-seize”
Related Questions
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