Go back to the engine and remove the engine cover. Have a helper move the warm up lever or handle so you can ID the throttle cable.
Remove the throttle cable attachment point at the end of the cable and take it off the linkage.
Have a helper move the shift lever into forward while you move the propeller clockwise with your foot. The shift cable will move first.
Observe the throttle cable, see how far it moves.
Once the cable has moved as far as it will go grasp the throttle linkage where the cable was formerly attached and move it to wide open, engine is OFF. See if the cable and the linkage moves the same amount.
If the cable and linkage is off my a very small amount you may be able to adjust it at the engine. If the cable doesn't move or very little the problem is the cable is bad or there is a problem in the control box.
If both the cable and linkage move the same yet the engine doesn't accelerate you could have clogged carburetors, ignition failure or even a powerhead problem.
Post back what you observe and we can go from there to narrow this problem down.