Hello. I have a Mercury 150hp Short shaft (16in). The lower unit wouldn't shift into reverse. Mechanic said the reverse gear was bad. I couldn't find a lower unit to replace this one. So, I bought a good working lower unit with a 20" shaft. Is it worth while to switch the shafts? Or is it better just to rebuild the 16inch? The engine itself runs fine and has newly rebuilt carbs. Compression is 119-120. I want to make this engine complete, but want to find the least expensive way to make it "turn key" so I can sell it someday.