shifting cable

[striperguy]

i purchased a new shifter cable today and put it on, i put in nuetral and adjusted the cable. when i engage the throttle it seems to short at the motor it wont go into gear forward or reverse. it will move but not enough to engage. there seems to be slack at the shifting arm. i can adjust the cable up and it will go into forward gear but when i pull throttle to rev it lines up in the nuetral position at motor. am i not doing something right.