9.9 throttle control loose

[hastingsml]

My 2000 yamaha has the twist grip throttle on the control arm. Yesterday the entire piece that turns was loose and it would actually pull completely off the arm. I can look in the end and see the spiral groove that moves the throttle cable. On the shaft that remains I can see the things that slide in and out that controls the speed. I know the piece must rotate but I don't see anything that holds the grip onto the shaft. What holds this on?

[boats.net]

It's held with a screw, number 15 in this diagram Yamaha Outboard Parts 2000 9.9MLHY STEERING Diagram

[hastingsml]

I think this diagram matches my outboard.

It is a little different than the one you posted.

Yamaha Outboard Parts 2000 F9.9MLHY STEERING F99MH Diagram