Congrats on the new to you Sonic! Very nice boat. Yours may not have a dipstick in it. If you have a large hex nut on top then you will. There should be a 1/4" pipe plug in the top, or a dip stick, which is a vent and there should be one in the front of the case about 1/4 of the way up from the bottom, when you take the lower plug out the oil should be to the bottom of the threads just coming out. If you dont have a plug 1/4 of the way up then you can drain some by removing one of the lower bolts on the front cover. As far as the bearings in the rear of the blower they are sealed roller bearings, no oil. Now, the oil that Merc uses is high perf gear lube, the green stuff. Some people run mobil 1 or there specialty gear oil. As far as how much, its not much something like a few ounces. I'll try to find the amount if there is one.