I know I have posted this before, but I have still been working on this to no avail! I swapped out a 1974 Merc 120 for a 1995 Mercruiser 181/3.0 140. I am using the 1974 Manifold and Carb so that the engine will mate with my 1974 pre Alpha outdrive. I have replaced everything, rebuilt everything and tuned everything that has to do with Fuel or ignition and nothing has affected the symptom. My symptom is that the engine will not go full throttle. It is not an RPM issue, although it will not go past 3200 rpm smoothly. When you bury the throttle out of the hole, or even go WOT on the trailer quickly, you can hear the bogging. As far as my diagnosis is, the engine is too rich when going past 3200 rpm. I tested this by running the boat at 3200rpm and then gently trying to close the choke to see if it was too lean or too rich. It's way too rich. The boat will run all day long at 3200 rpm and below. It really runs like a top. My issue is when I go above 3/4 throttle. This is my question... What, in my setup could be making the mixture too rich? I am talking WAY too rich? The bogging is so bad that if I don't back off after about five seconds, the engine will die. As soon as I back off, it will run smoothly again. I have rebuilt the carb, cleaned fuel tanks, tuned everything. I am wondering, is the 1974 Merc 120 carb too small in CFM to run the 3.0 liter? Is the 1974 manifold the bottleneck? I am just baffled, as is everyone I talk to at the local shops. We just don't understand why at a certain throttle position, the engine runs extrememly rich. I have even tried different main jets.<br /><br />Help!<br /><br />Thanks, Nicholas
