Strange oil leak Yanmar Saildrive SD50

[bugs]

I have oil leaking where the saildrive meets the hull. It is weeping from between the large circular flange that is bolted to the hull.
I assume it is leaking from the leg and making its way out at this point. At first I thought it may have been engine oil dripping from joint of the flywheel but its got that very distinctive smell of synthetic gear oil.
Is this a difficult repair? Yanmar 4JH3 39 hP with SD50 leg.

 

[BlueChip]

Are you 100% sure you havent just lost the O-ring from the yellow filler plug and oil is blowing out when the gearbox warms up and is running down the back of the gearbox.
Its happened to a few on here and is sometimes difficult to diagnose until you know about it.

 

[bugs]

o-ring

I wish :-(
I scrubbed it all clean and watched carefully.
It looks like I will need to dismantle the leg/hull flange.

 

[magdalena]

Was it a difficult repair? I now have something similar...

 

[Mrnotming]

Have youtightened the flange bolts to the mfgs recommended torque? might cure it if clamp bolts are slack?Sorry not a yanmar owner, have a volvo 2030 with saildrive.Probably not the answer, just trying to help!