I have a 8 h. p. mercury long shaft S/N ob103614. Need help in oil change. There is a drain plug on skeg like most motors have,but no top plug. There is a stove bolt (about 1/8 inch bolt} just under the water pump. Is this the top plug or does this hold something in place and if I take it out will something get screwed-up. I believe this is a 1987 model. This hole would be at the very top and if oil was filled to it, it would not leave much room for expansion. There is a small round place where the top plug usually is but there is on hole. Thanks for any help you can give me.
