Calling you back with the real answers you are looking for (I think) - bearing clearances were .0025 on the rods and .0031 on the mains. Those were taken with a dial bore gauge and a micrometer.
Instead of using like an HX bearing - the bearing housing bores were oversized to: mains .0018 over and the rods were +.0008 over. Crank measured: mains 2.749 and rod journals 2.1998.

I do have oil temp and pressure gauges. 70 psi normal running. Oil temps were always around 185-190. I never ran the boat over 5000rpm.

Oil was changed 4 times in the 20 hrs - it never smelled burned, and there was no burnt oil smell when dismantling it.

I guess i need to ask - is this something I did wrong?

What parts?

Clevite 77 B-1 bearings
clevite H bearings
Manley Rods
Morel Lifters
JE/SRP Pistons
Cranks were not out of round, tapered or worn.

I didn't choose the parts - left that to the expert I paid.

Forgot, Side clearance on the rods: .0240

is the crank old school cross drilled?

all good parts,and clearance,s all good.oil pressure&temp good,and changed oil more then enough.what does your engine builder think went wrong?

Is this an N/A motor ?

i don't like running 50wt oil, cold and thick oil will do same as no oil. it needs to flow to get into bearing surfaces. the forward bevel can also pick up oil in bearings and push the oil back into oil passage instead of onto bearing surface. i consider 50wt to be oil towards end of usable engine life, thats from 30+ years of working on engines.

well... another mystery. everything is correct. the parts are good, the clearences acceptable. it was assembled by a skilled professional and it never ran higher than normal cruise speed at perfect temps and pressures yet the bearings in the rotating assy are scrap in very short order.

for me, it is hard to accept that the bearings are turning to scrap with perfect temps and pressures or any other meaningful symptoms...

i guess all i would ask at this point is if these were new assemblies or pre esisting rebuilds...

He paid for new parts. What he got in return........ I was burned by a local mechanic in named David Pou at DP Marine in Hilton SC. Beware!! (fitting name). After phucking with the heads and intake I assumed there would be problems in the block. Suprise suprise.....

The motors were N/A.

Once again, the crank was reused it had just under 100 hrs on it. He madde the decision to reuse it. Everything else was new. He did all the machine work.

I know it seems really hard to believe these ground troughs could be the culprit...huh.

In looking for someone to build my new motors, 2 of the 3 engine builders said the cranks were scrap and they would never do that - one said they wouldn't do it that way, but they were not ruined.
I am waiting on some information from the clevite engineers, but it seeems that the engineers that design and work with cranks everyday would know what they are talking about. If this modification was a good idea - don't you think it would be incorporated into every crank produced - maybe even one. I can't find any mfg who makes a crank with some grinding across the oil holes in the main and rod journals.

Moving on here are pictures of after the one time we took it to 5000rpm. Oil blowing out of the seal at the rear china wall. Left the paint on china wall and the sealant never bonded. Paint peeled off and leak started. Talk about surprised.