GT-40 oil drip

[Ricky95-196]

Alright everyone, here's one for you. I have a 95 Ski Nautique closed bow, with a GT-40 only 548 hours. Just near the end of the year i noticed only after the boat sat for a long period after use it had a small oil drip. It is coming from between the engine and transmission bell housing. I wipe it up before hitting the lake and there is no oil drip after the day on the lake but again after sitting for the week it has a spot under the engine. It is definitely oil. The longer it sits the bigger the oil spot.
So my question is, where is it coming from. My only 2 thoughts were either the rear main or the oil pan gasket. But with it not leaking while in use like a day out on the water and only on trailer sitting i am leaning towards the oil pan gasket.
This is very frustrating because I baby the boat and find this.
Any thoughts and input is going to be greatly appreciated. Also any advise or experience with puling the motor to fix either problem will be greatly appreciated. Thanks for reading and thanks in advance for the help.

[Westlotorn]

Your drip could be oil dripping down from the top of the engine, back of the intake manifold, valve cover, Etc.

The other possibility is the rear main seal. If the rear main is leaking you will need to remove the Transmission and replace the seal.
Federal-Mogul makes Teflon rear main seals that would be a lifetime zero leak replacement. Probably a $50 seal rather than a $25. seal but worth every penny.

A search in the dark with a black light can reveal the oil leak source. New Oil will glow purple in the black light.

[Celle]

Hey, we had a similar problem with our GT40, but i was coming from the tube for the oil change that is attached to the Oil Sump.

Clean everything with brake cleaner and wait 2-3 days to see from where the oil is coming.