mg86ta

Hey everyone, I own a 96 780 and I'm having a problem.. When i bought the ski the first couple of times i took it out, no problem.. Then I took it out again and from a dead stop, when you accelerate the motor revs up, theres a little vibration it feels like and it doesn't go anywhere.. And once you plane out it moves no problem at high speeds.. It sat for the winter, and I just took it out and it didn't do it for the first 4 hours of riding, then it came back.. Is this a bearing problem? I looked at the impeller and theres no damage or blockage. Thanks!