Merc. 850 throttle problem

[jeffrayy]

I have a merc. 850 (early 70's) and I'm having some problems with the throttle. It starts up fine, idles fine, and goes in and out of forward/reverse fine. The only problem is that there is not a response when the throttle is pushed all the way forward. The boat only wants to go about 5 mph. If you take off the motor cover you can see the throttle cable pushing to to the peg. Just no response in the motor.

I know this may not be enough information, but any ideas would be greatly appreciated.

Thanks!