1967 Johnson 20 HP FD 21r shifting problem

[traelar]

SO i bought a boat with a 1967 Johnson 20 hp motor the motor runs great but i realized i was only able to go
half throttle out on the lake. so i messed around with it yesterday and i realized when you shift into forward and engage the throttle it stops at about half throttle. then i noticed if you manually turn the prop a little bit then the shift lever goes all the way forward and i can open the throttle all the way. what can be causing this? is this a lower unit problem? i can post pictures with more info tomorrow when i am messing with it

 

[racerone]

??----Your first outboard motor ?---All sound normal and nothing wrong with shifting.------Propeller must be turning when you shift on a stand.------And if motor is in neutral you can not go full throttle !-----You need to install a new water pump impeller before using this motor.----Other checks as well.----A fine motor that you will enjoy if you give it some care and respect.