Throttle not opening all the way, starts at half way and gets nowhere near WOT

[Skippy18]

I have a 2000 mercury 50 4 stroke tiller handle. My throttle will not engage anything until half throttle and then there is not enough throttle left when I am WOT. It will not engage all the way and there is plenty of throttle left when I move it manually with my hand on the carburetors. When boat is in the water it doesn’t have enough power to even get on plane. It is not the throttle cable as I have just replaced both of them but I cannot figure out what the issue is. I am attaching pics and videos for reference. Anything anyone can help with would be greatly appreciated. If anyone has the same motor and can share photos or videos of what I have referenced that would be appreciated.

 

[Mc Tool]

"It is not the throttle cable as I have just replaced both of them"
Oooh ! I love it when customers say stuff like that .
Usually when something stops working after you have fixed it something has gone amiss . Im thinking you have to much free play on the opening cable . It is possible that the cable outer was not fully seated in the adjuster and now is giving the extra free play.
Just go back over what you have done methodically and give it poke and eyeball and Im sure you will find the issue AND its unlikely there has been damage done ( unless you heard a snapping sound you forgot to tell us about )
One thing , did you compare the old and new cables to make sure they were the same ,wouldnt be the 1st time a customer has been sold the wrong part .
I cant get the vids to open so I cant see but if you start at the carbs and work back along the links/cables towards the tiller grip and you will soon see where the movement is lost