Yamaha vmax wont go into gear

Yesterday out on the lake, motor started acting kind of strange. I ran to first spot and when I got off plane and came to an idle the motor starting sputtering. Sometimes it would die. I could run without any issues. This happened about every time I moved to a different spot. After my last spot, heading back to boat ramp, while going full speed I suddenly lost all speed and the boat stopped. Motor still running, but now could not go in forward or reverse. Do these two issues sound related, or does it seem I have two separate issues. Also, what are thoughts on not being able to put it in gear? I can move the lever forward and back, but the motor doesn't engage. Sometimes the lever won't go forward or back, but most of the time it will go either, just doesn't put the motor in gear.

I should also mention, no lower unit work has been done for several years, so know this is not associated with a recent repair.

I maybe an easy fix, throttle cable(s) at engine can break or come loose. Happen to me.
I can't remember the details, but I'll look it what did.

To look, take off the cowling and look at the throttle cable while somone moves the throttle lever back and forth and a problem will be pretty evident

Sounds like two things. 1) Shift cable is bound up and not working. 2) Engine related, but without the year and type, hard to point you in a direction. EFI or HDPI? Pull your lower unit and see if you can manually operate the shifter and engage the gears. If you can, then it's the shift cable. Maybe it got loose at one of the ends at the keeper. If that's not it, then it's something internal. The cogs inside are pretty heavy duty, so if something messed them up, you would know. Once you post more motor info, I may be able to point you in a direction.

This is a 2-stroke HDPI, 2006 VZ300TLR motor. I have never pulled a lower unit off, so I need to see if there are some youtube videos so I don't mess things up further.

Did you pull the drain plug on the lower unit?

Gary had a good idea. Drain it first to see if you have any metal. If so, it's internal problems most likely. Pull the prop before you drop the lower unit. Both will make it a little lighter to maneuver. If I remember right, I used a close end wrench on the shift shaft you will see sticking up to test shifting. Experiment with the size to find the right one.

Had a 2004 HPDI that would not shift and found a small screw wedged at the shift shaft top.

I will check under cowling first, then drain lower unit and remove it and see if I can tell what is going on. Thanks for comments and suggestions.