engine bogs going up a hill as if you need to gear down

[Fasterblaster]

I just picked up another Bravo for the kids. When going up longer hill, it acts as if it needs to gear down. Is this caused by the primary or secondary?

 

[sol-sask]

check your secondary out seems that your belt is not getting backshifted fast enuf......should be tightened to about 70 degree twist

 

[yamyrider]

check the secondary, may have bad bushings or very dirty clutches.
Your clutches may not aligned properly.