One thing to look at is valve guide to valve stem clearance. Sometimes during a rebuild this can be overlooked by some, knurled valve guides, worn valve stems can consume oil. If a leak down shows good, you can check your intake valves with a bore scope after removing carb. Valves should be clean with no oil or deposits. The exhaust valves may show a little oil on stem, this is ok. I usually remove the spiral ring on the exhaust valve stem seal to increase lubrication to guide and stem.

+1. I had the same problem. Change Your oil an give it more break in time. I don't think Your rings will seat with Royal Purple. Artie

thanks for the replies. im gonna try switching oils to see if that makes a difference. Would like to stay with a synthetic. so ill try the Mobil one first. and see how it does. I know the valve stem seals were replaced. ill have to ask my engine builder about the guides. Next time i do a leak down ill warm the engine up first to get a better read.
i would think the engine would be broken in by now. ive put 40-50 hours on it since.

did you break in with the royal purple ? if so there's the problem...NEVER break in with synthetic....always use std for a while...I use rotella, and now I don't even go to syn any more...waste of $$$ my .02

Some times improper break in can glaze the cylinder walls. If you haven't run it at all with break in oil, I'd do a warm leak down and see where your at. The only thing I've heard done once the cylinders are glazed is to pull the motor, tear it down and hit the walls with a fine stone. Maybe someone else has been successful with another process. On the Mobile 1, it's good stuff but don't run the grades for modern motors, use the V-Twin or Diesel versions. Better yet, run Amsoil Dominator.

I use Castrol GTX 20 W 50 in my Merc HP 500 carb engine, seems to do fine, however they are known to loose about a half a qrt when run hard, mine seems to do fine though. I have some Brad Penn I recently bought, but may stay with the Castrol so far it's been fine.

Leakdown on a cold engine doesn't really tell you much IMO. Except maybe the condition of the head gaskets.

I agree with others to switch oil and see what happens then go from there.

The engine was broken in using a specific break in oil made by Lubeatech Advanced Technologies. LAT 20w50. Engine was warmed up on the dyno and we made 7 pulls to 6k rpms on this oil. After the dyno i changed the oil to royal purple and dropped the engine in the boat.

It does seem to burn more oil when im running it harder. My normal cruising speed is 3500-4000 rpms. and at WOT i can spin it to 5400. but it likes to drink way too much fuel at anything higher than 3600. so try to keep it reasonalble.

Im really not ready to pull the motor back apart less than a year later. Figure worse case might foul some plugs out. So if switching oil brands doesnt seem to help ill just let er eat, and keep checking oil level

Let us know your results after getting rid of the Royal Ripoff Snake Oil . We may be able to save someone else some of their hard earned money . :helmet:

an easy indication of worn valve guides is after the engine is fully warmed up, shut it off swim around for an hour then watch out your exhaust as you start it back up if you get a brief puff of blue smoke your guides are worn