How to fix my throttle on my boat?

Your problem sounds like it only needs to be adjusted properly.To do this remove both cables from the engine first. Then shift the engine into forward gear.After this shift your control box into forward at full throttle.At the back adjust the shortest cable(this is the shift cable)so that it fits on the engine shift bracket easily and hook it up.Once you have done this,have someone shift it into neutral.Then as they slowly shift it into forward turn the prop on the motor until it locks into gear.Mark or remember where the handle is on the control box when it locks into gear.Now do the same from neutral to reverse and see if the distance is the same.If not adjust the brass barrel on the cable until the distance is the same from neutral to forward and from neutral to reverse.Then hook your throttle cable back up and you are good to go. Hope this will help you,good luck.

Maybe you have them hooked up backwards. The throttle is running the shift and the shift is running the throttle. Will it go into reverse? Release both cables and see which one moves first. That one should be the shifter. Pull the throttle back into neutral and shift the motor into neutral. Adjust the cable end so it fits the motor shifter without any stress. Next do the same for the other cable. It will be either fully extended or fully retracted. Fit it to the engines throttle(asumining this is not a new marriage)- Now- spin the propeller by hand and have some one run the shifter.(you know not to have it running -RIGHT) You should feel the clutch engage with a clunk-next check the throttle is opening all the way. Now do the same for reverse-don't expect the throttle to open completly in reverse. And thats the best I can do with out knowing if it's a ski boat or a crab boat.