How do I change the oil in my motor. At the bottom there are 2 screws which the guy I got it from told me is where the oil goes. He told me what to do but I should have wrote it down cause i'll be damned if I can remember. Can anyone walk me thru the steps to changing the oil? ITs a 1958 Johnson seahorse 18hp.<br /><br />Thank you,<br /><br />-Jay