I had a tiny hole rusted into a timing cover… paint chip on the outside and rusted through just in one tiny spot. the rest look perfect. Could happen on an oil pan too (if steel).

chased my tail on that for a while

I thought about that but it doesn't leak all week. Oil level doesn't drop. In my other post I saw oil on the 2 back pan bolts.

35,
Get a bottle of UV Die at your local parts store along with a UV flashlight if you dont have one already. Put that in the oil before you run the boat again. Oil can migrate in ways you would never believe and the die will help you figure out where it is coming from.

Another option is to find a local automotive shop with a "smoke" tester for finding emissions leaks. Have them smoke the engine and see if that shows anything. Similar to what your engine builder wants to do but with smoke to find the leak.

I just put the dye in and put the glasses on and used the special flashlight and it is coming out of the back 2 bolts and a little tiny spot on the dipstick tube on the dipstick tube entering the pan.. I did this idling. I'm gonna use the boat Saturday and see if everything else shows up and I might even put dye in the other engine just to make sure. Like I said in beginning I need to pull the motors again. (BOAT)Break out another thousand.

Yuk, I have heard mixed results on the one pc oil pan gaskets. I have not had an issue with them but some guys do. I have been using the Fel Pro ones. One of my friends at another machine shop has started smoke testing every engine right on the stand. Thinking about getting a smoke machine and doing the same thing. Running them on the dyno every time would probably catch little things too.

My engine builder is going to pressurize the engine with air low pressure under 5psi and the look for leaks with soap bubbles. Seems primitive to me but that is his way. I told him I put the dye in and i told him what I saw. I will order the Fel pro gaskets.

That's basically the same thing that the smoke check does, just not as messy

So today I went down to the boat at the Marina and I got into the right side of the engine, reached all the way down to the bottom of the bellhousing...wow oil at the flywheel cover. This is the 1st time I noticed this. Rear main seal now?. He installed felpro rear main seals the blue ones. Unless the guy put them in backwards? So I checked the oil level and it was only down maybe 1/8 of a quart @ 1 hour run time
Is it possible that that breakin crankcase pressure blow by caused the pan gasket to open and let out oil in the back corner of the engine. Windage shooting oil onto the flywheel because it seems like the oil leak is getting less. My total hours are 12. Maybe there was a lot of blow by in the beginning and now the rings and everything finally seated.

I always stagger the seams on a 2 piece seal you don't want the seams parallel to the main cap and block, be interesting that you find.

Your engine isn’t sealed tight so I doubt that crankcase pressure would be the cause.

Are you sure the pan bolts are all tight?

You’re positive that there isn’t an intake leak? Or maybe a leak at a galley fitting up top?