Throttle and trans cables

[88falcon 0]

Hello all I have a 1988 20' ski centurion falcon, ford 351w.  I've had issues with the throttle/ transmission when putting it into gear it immediately is giving throttle.  I've adjusted the cables as much as I possibly can and it's better but it's not normal, the throttle is maxed out when the lever is only half way down basically 90° to the floor or even with the neutral detent button.  If I disconnect the throttle cable from the morse controller, I can't move the lever all the way down.  

Does anyone know what length the throttle and trans cables are suppose to be?  Right now both are 17' 

Or does someone know how to measure to find the length im suppose to have?

Thanks