2019 jet unit question

[Riverroo]

2019 242 Limited S jet unit question.Not sure what this nipple on top of jet unit does, but left unit is missing bolt that goes in top of it.


Left jet unit missing bolt

left jet unit top view

Right jet unit with bolt.

Top view of right bolt.
Not sure what these do but left units missing bolt? But says it's supposed to be bonded into nipple? When I feel inside of nozzle I can feel small hole below where bolt would be, no hole on inside nozzle on right jet unit though?? Any help appreciated the tech @ dealership where we bought boat said on phone not sure why these do....

 

[Riverroo]

Update after getting boat on trailer was able to see both nozzles have the small hole below on bottom of where bolt is. Not sure why they are there but as stated earlier left jet unit is missing the bolt. They are bonded in and I found replacement on Yamaha parts site, but wondering what I should use for bonding it back in any ideas wold be appreciated. Also wondering what these bolts on top of jet unit are even for???