Well, it's not hard to find a leak to be honest if it's leaking that bad, now did they dyno it? fire it on a stand and it was ok? then in boat it leaks? or did they put on valve covers and pan or did you and buddys?

if it is building that much crankcase pressure that's on them, not you, ask them what the ring gaps are and how they finished cylinders..

in what form did you get engine back? carb to pan? longbock? shortblock?

I would not let the same guy do the work again. Shipping engine is not that expensive compared to what you spent. Dyno time should be 100hr plus fuel oil. You will be in court over this.

I am just a backyard engine builder and have never had a problem with oil leakage. You need to take it somewhere else.
OH and BTW I don't build stock engines. the latest is 598 cubes at +800 HP ( engine is designed and built using parts for 1500 HP as I plan on adding a Procharger )

Before I mention I'm going to see how they handle this, they may comeback stellar and I'm just jumping the gun but I'm kinda concerned about where this could go.

They more than likely will come back with silicone gooped on them . A good builder would not have sent them out this way in the first place. Craftsmanship and pride or just money in his pocket.

I am a little confused. you said your mechanic said that it may be building too much pressure and needs valve covers with vents. how is the block vented now? does it have a pcv or what system for the crank pressure to vent? if it has valve covers with no vents I can see how it would build pressure in the block and push oil out. also what are you sending out with the engine and what are you keeping as far as external hardware? when ever I run an engine in on my test stand I use all the lines and coolers, etc from the boat so if there is a leak in something it will show up on the stand instead of the boat. more details are needed on what has been done on what parts.

My mechanic is so good I go to him every week!

For about $20 you can get oil dye and a black light and see exactly where that oil is coming from. It worked like a charm for me.

You have Procharged engines, right?

We need more info please

Sorry to hear that you are going through this, definitely not fair, and all to common in the marine world.

But let's make sure we are not missing something here.....

Sounds like you decided not to dyno the first time? Running a freshly built engine on the dyno has WAY more benefits then recording power output, like tuning, properly breaking in, and checking for LEAKS ;-)

Hopefully your builder stands behind his work in some way, but that doesn't necessarily mean free, since we don't know what your original arrangements were. At the very least I hope you both have better communication in the future.

OSO brothers can't guarantee everything, but we will offer as much advice as possible to help everyone protect themselves from issues like these.

Good luck

yes, were engines complete, or did you put on pan, valve covers etc ? if you are loosing that much oil that quick should not be hard to find, sound more like a oil line or fitting ? put a go pro camera in there and run it...