This shift system is the most pi*s poor designed piece of crap I have ever come accross. No wonder OMC went bankrupt with the crap they designed. Anyone that buys a boat with an OMC drive is just asking for trouble.
Ur, blame Volvo Penta, not OMC. They designed the Cobra drive. Still make 'em as the SX. Not a bad drive, just misunderstood.
I'm guessing that you're missing a step if you say you followed the Hastings directions. As good as that site is, it really offers nothing more than the shop manual as far as adjusting the cables and the shifting.
1. Be sure the lower drive is in neutral by turning the prop. There should be no binding and it should spin easily. If you adjusted the shift rod, you're good.
2. Be sure the shift handle is in neutral. Stupid, yes, I know but some handles appear to be in neutral when they are in fact, not.
3. Take all the cables off the engine.
4. Set the bellcrank angle using a clear plastic elementary school type triangle. Set the triangle against the housing and set the bell crank arm up against the bottom edge of the triangle so that the bell crank is at 90. Do not move the bell crank from now until you have completed the cable adjustment.
5. Inside the boat, pull out the cable until it is 7 9/16ths (within a 32nd) from the end of the brass ferrule to the center of the hole. This is critical and you must not mess it up. A clear day glo plastic ruler from CVS is the right tool.
6. Back at the bell crank you may now install the egg shaped nut on the cable. turn it until it stops in alignment with the fixing bolt hole. Install fixing bolt, and put a lock nut on the cable end.
7. Inside the boat, reattach the lower shift cable to the lower pinion. Loosen the upper pinion (the one in the slot) so that it is free to move. If the lower cable has an adjustable trunnion, adjust it so that the upper cable will meet its pinion about halfway in the slot.
8. Tighten upper pinion in place and attach the cable with a cotter pin.
That's all you can do. It should shift pretty well at this point as long as you have the idle set low enough and your ESA module is functioning. Be sure the micro switch is engaged when you operate the shifter, should hear a little click when you tug or push fore and aft on the upper shift cable pinion. Dry test to see if the drive goes into forward and reverse.