When we bought our Maramu in 2013 we noted that the previous owner filled the gearbox with 90w gear oil when he rebuilt it prior to sale. There was a small stain on the deck from an occasional drip. The surveyor pointed it out, the seller and broker acknowledged it, and no one seemed alarmed.
The drip stain is easily cleaned and intermittent. No more than a few drops a week and often nothing at all. It seems to be related to heat from direct sun. It does not seem to increase with use of the motor. But I wish there was some way to check the oil level inside.
Since I did not do the service work, I cannot attest to the seals and O ring. The use of the gear oil makes sense but I would say you might expect some drips. Perhaps this is why Amel used grease.
Thanks for this discussion. About 4 weeks ago I was about to bring up this subject.