Last weekend I had my boat out first time this year. New premium fuel. Its a 2001 Yamaha 70 hp with a jet foot on a 17 ft flat with a jet tunnel. I was running upstream while watching the gps speed on my phone and was about 2-3 less than last time it seemed, but this river has more current than the last i was on. I went around a bend facing west blinded by the sun and almost went to a dead stop from 20 mph or so because i hit something. It took awhile to get unstuck from the sand bar but when i finally got going i noticed i couldnt get going about half throttle or so. I found at home i chipped up the impeller a little and put a couple more grooves in the wear ring, but nothing bad. I swapped them out for a couple in better shape and tonight i took it out again.
It turns out it wasnt the impeller or wear ring, it wants to cut out at above half throttle. What would that hard hit have done to cause a fuel/air issue because thats what it kinda seems like. Im far from a mechanic, just gives me that impression.

I had a similar situation in Alaska many years ago, seems like the porcelain on a plug cracked and was shorting out. Try changing plugs and see what happens. A cheap test!

Impact has caused something to come loose. Glad to hear you weren’t injured. 20mph to zero is enough to normally through you out of the boat or at the very least into the front of the boat.

If you start to get cavitation as you increase the rpm’s then it’s a jet problem (usually some kind of foreign material around the screw or grate). Loss of rpm is strictly due to a motor issue.

I always have on a pair of polarized sunglasses if the sun is out when I run our rivers. Too many logs and big rocks.

Trust me I wouldve went airborne if this was a tiller. My phone flew and I smashed into the console.

That type of force can sometimes transfer the force through cables and into your throttle cable box. Check your throttle cable box sometimes theres a piece of plastic gears that will break down causing issues.

I had 1 do similar once.
It was a rev limiter got set.
Had to unhook the battery, remove all power for a spell and it reset the limiter.
Werent a Yammy tho.
Good luck.

My thoughts are inline with Newhouse114. It's very possible that it's just a coincidence that the pump issue and the throttle issue happened at approximately the same time. Change your plugs and see what happens.
Did you check your plug wires to see if one of them jarred itself loose?