Yamaha 6x0 remote control box

[nightowl66]

I have a Yamaha 6x0 remote control box. I think the throttle opening adjustment stopper bolt needs adjusted. When I go from neutral into forward, I have to move the throttle lever quite a bit before there is a increase in rpms. The manual shows the adjustment bolt. Would this be what I need to adjust?
I am able to reach the bolt, I can't see it, it felt like a 3/8" wrench fit on it. I can't tell if it is a slotted screw in the end or what I need to adjust it.
Any help is appreciated, Thanks