Is it OK to use a small hub mercury propeller on a large hub gear case?

[Bumblebeeman]

I have a 1991 XR4 150 that I ruined my nice narrow hub 4-1/4" gear case. I replaced it with a regular 4-3/4" 2:1 gear case from EBay. I have a highly accurate digital tachometer and know I have to limit the throttle going from a 1.78:1 to 2:1 gear case and did not go over 5600 rpm. I used my same narrow hub 24" pitch Laser II prop with the thrust washer in the enclosed pictures that is now broken, shown together with a standard Mercury P/N 13191 thrust washer for comparison. The other half of the broken thrust washer was lost. I cannot find any part or manufacturer's number, but that may have been on the other half that was lost. I used to have a 2001 Johnson 150 on a different boat, and a 1994 Yamaha 150 on another boat different from that, so this thrust washer may have been an OMC or Yamaha part I had sitting around. Does anyone recognize what make thrust washer it is from the front, rear and side views in the pictures?

My question is, could the thrust washer have broken because it is wrong to use a narrow hub prop on a standard diameter lower unit? Could the thrust washer have broken because it is not compatible with a Mercury prop shaft? In the side view picture of the broken surface there are different colored areas that make it look like maybe it was cracked for a long time corroding the surface, and only the shiny portions finally broke all at once out on the water. That might make the whole small hub prop / large gear case thing an unrelated coincidence. If that is the case, is it OK to use the 13191 thrust washer and the small hub Laser II on a standard diameter gear case?

[FORBESAUTO]

I’m guessing the washer broke because not a merc washer. The taper has different angles on some manufacturers. You can run the small barrel prop on the larger diameter lower with no mechanical issues. You may run into cavitation issues on take off due to more exhaust coming around barrel of prop and causing cavitation at blades.