1983 80 HP Mariner Outboard troubles

Good Evening, <br /><br />I hope someone can help me out...<br /><br />I have a 1983 Mariner 80 HP outboard (SN: 6472225). Here's my story...<br /><br />The engine runs beautifully out of water, when I put it into the water, my troubles begin. I start the engine and it idles fine... As soon as I put it into reverse, it dies... To keep it from dying, I have to intermittantly choke it to keep it running while in reverse. <br />Then when I go forward, I have to keep choking it at low speed to keep it running. When I open it up, it bogs to the point of dying. I keep it from dying I have to choke it. It will finally catch and then I can open it up all the way. <br /><br />I've had this problem for quite some time, and have had it into the shop a few times. <br /><br />First was a tune up. Same problem while in the water. Mechanic didn't have it in the water at all.<br /><br />Second, I had the main switchbox replaced because it was throwing incorrect voltages. Once replaced the voltages were correct.<br /><br />Still the same problem in the water. Mechanic didn't have it in the water at all.<br /><br />Third, I went after the fuel system. <br /><br />1) replaced fuel tank<br />2) replaced fuel connector housing<br />3) replaced primer bulb<br />4) replaced engine connector housing<br />5) replaced fuel filter<br />6) replaced fuel pump gaskets<br />7) had carbs rebuilt/cleaned (mechanic said they were fine except for a piece of junk in one of the main jets)<br /><br />Finally, I am having my mechanic check my timing and compression. It's in the shop right now for that. I am hoping that this is the problem, but if it isn't the problem what should I look at next??? Even my mechanic is at a loss.. I hope that the vast knowledge within this forum could help me out.