First, I tried search and got 48 pages of hits. I have a '72 Mercruiser controls throttle/shifter. It has a black button on the shifter pivot to make the shifter throttle only. I found the set screw that releases the handle, but the assembly seems to be stuck by the push button. I've looked all over the shifter box, but can't find a way to release the button. The handle has to come off to get to the shifter box mounting screws. How does it come off?