My 1996 Mercury 225hp Carb 2 stroke has recently begun leaking a thick oil (blackish/brown) from the port and starboard drain holes in the driveshaft housing just below the fin on the housing. I have a long shaft so these drain holes are about 4" above where the lower unit attaches to the driveshaft housing. I at first thought it was from the lower unit as I had replaced the water pump myself about a month ago. However, I have dropped the lower unit and taken it to be pressure tested and it was fine. Additionally, after looking at a schematic this drain hole passage way is between the driveshaft housing and the exhaust tube and therefore, I believe, isolated from a lower unit oil leak. I also compression checked all cylinders and they were fine. So my question is can this just be unburned gas/oil in the exhaust. It seems like an awful lot of oil to me to be just that, it will drain for a good 3-5 minutes after the engine is shut down. (I do have a long trip at idle, 20 minutes in and out from my dock, and the motor is left up at full tilt while docked). Could there possibly be another problem....oil pump, carburetor float, air leak in fuel line causing excessive amount of oil to be pumped in, etc. The motor smokes at start up but runs fine after a few minutes....the plugs were "wet" with oil when I did the compression check but not to the point of being fouled. Thanks for any help you can give me.
