yamaha 40 hp 1993 feels like slipage

hello all . my 1 st post. i hope some one can explain something to me. i was out in my boat. motor running fine. i gave her full throttle to see how fast i could get her up to. but when i gave full throtttle seems like she reved up but i wasnt really going as fast as i should have. but when i noticed this. seems like the prop caught with the motor and she moved on really well it happened a couple of times if i take off slow and then speed up seems fine what could the problem be any explaination would help thanks

[boats.net]

If there are weeds caught on prop and it's not trimmed too high or cavitating then the hub in prop is probably spun and need to have hub replaced.