maybe 1 a spun prop
2 check fluid level of drive
3 check cable adjustment at both ends
4 shift linkage at drive
once moving does it ride normal?
happen in reverse also?
Go out back and check to make sure the cable is fully engaging the drive. Take the 3 10mm bolts off the upper cover of the drive to access. It sounds like you are not fully engaging it and you cable probably needs adjustment.
Nope,
Is the shift cable actually pushing the shift mechanism all the way into gear?
With the engine running, move the shifter into gear and see if the shift mechanism will turn any further by hand.
the clutch slips in fwd and not in rwd. i will try to mod the clutch so i can use it for a few month more. i think i can grind the tip of it so the clutch can go deeper.