Have a 1999 yamaha 50hp 4stroke outboard engine. So I poured engine oil in the top crankcase fill plug, needs 84.48 us fl oz got half way and now it's draining down to the lower end and pouring out the prop. Checked the lower end and is not mixed with engine oil and lower end oil. What could this be? Top end, leading to lower end crankshaft seal? Prop shaft seal? Thanks