Patent ID: 7674146

Claim:
A propeller thrust transmission device for a watercraft propulsion device, the propeller thrust transmission device comprising: a propeller shaft including a taper portion having a larger diameter end and a smaller diameter end, the larger diameter end having a larger diameter than that of the smaller diameter end; a spacer including a taper hole having an inner surface corresponding in shape to an external surface of the taper portion; and a propeller attachment device arranged to be engaged with the propeller shaft through the spacer; wherein the spacer includes: a first half including the taper hole arranged to engage the taper portion of the propeller shaft; and a second half separate from the first half, the second half including a forward end surface arranged to engage the first half of the spacer, a larger diameter portion extending from the forward end surface and arranged to engage an outer peripheral surface of the first half of the spacer, a rearward end surface arranged to contact an end wall of the propeller attachment device, and a smaller diameter portion extending from the rearward end surface and arranged to fit into a hole in the end wall of the propeller attachment device, the larger diameter portion of the second half having a larger diameter than that of the smaller diameter portion of the second half; the propeller attachment device includes: a boss integral with a blade portion of a propeller; a bushing mounted inside the boss, the propeller shaft fitted inside the bushing; an elastically deformable damper member provided between the boss and the bushing; and a concentricity maintaining ring provided on a forward portion of the bushing and extending between the bushing and the boss so as to maintain the concentricity between the bushing and the boss; and the forward end surface of the second half of the spacer arranged to engage the first half of the spacer is substantially aligned with the smaller diameter end of the taper portion in a vertical direction.