Dt60 clutch?? All revs no movement

[Firemanpat01]

Hi guys , I have more problems with my DT60. The other night when I was in the boat I was traveling about 5knts when all of a sudden the boat reved its tits off and went into reverse . Although the gear shifter was still in drive forward I increased the throttle and it went faster backwards. I had to put it back in neutral then take it back to drive for it to work again, but it would only go walking pace any increase on it and it will rev like hell but not go anywhere .... Any ideas on what it is and how to fix would be greatly appreciated
Cheers patty