This is the angled spacer, Yamaha PN F4X-U471E-00.
This spacer is for 2021 - 2023 model year boats that are 20 foot and longer. Please check Babbits Online to see if this part is listed for your boat. These are located in the "Hull Deck Fittings" section for your boat model.
This spacer increases the angle of the mount by 7.3 degrees. The large end of the spacer measures: 0.625"
PLEASE NOTE: This is for model year 2021+ boats only (specific to the spacer).