Yamaha 90 Crankcase Leak

[52Alumacraft]

I have a 90 four stroke that I bought a year ago. After bringing it home from storage I have noticed crankcase oil on the cavitation plate. I wiped it off and tightened the upper plug but within a day it was back.

I'm pretty sure I didn't overfill it last fall when I winterized so I am a little confused about what is going on here. I'm also concerned that if oil is leaking out water will get in. Any thoughts would be appreciated?
Thanks,
JB

 

[clanton]

Re: Yamaha 90 Crankcase Leak

Probley crankshaft seal, Service Bulletin that covers this with part numbers. Rodbolt may share this info with you.