Originally Posted by snapmorgan

I had the exact same thing happen to me. Built a new 540 with a new block and crank and used the stock 502 mag oil lines and cooler. After 30 hrs noticed some loss in oil pressure. Main bearings looked terrible. Polished the crank, put in some new bearings, upgraded the lines and cooler and now 5 years later it is still running with no issues. Lack of volume combined with high oil temps is not a good thing.

Originally Posted by ctuck0659

That's actually good to hear inasmuch as it may suggest a reason why this happened. But my question is still why wouldn't the bypass valve compensate for the lack of volume going through the lines?

Originally Posted by 33outlawsst

Im guessing this is a twin application, any problem with the other engine ?? or did you loose them both...........what does your engine builder say happened, like Mike said were all just guessing not seeing any of the parts.

Originally Posted by sutphen 30

because when you actuall look at how big the hole is thru it,its small,,its about .310'.thats why.no volume,,great for cars and trucks,,not for boats.

Originally Posted by Black Baja

What head gaskets were used on the motor in question? I have a pair of 540 Merlins that were built in 2000 they still have the original oil lines, filter pad, block adapter and cooler from the original 1993 502/390 that came in the boat originally. Oil temp never goes above 150. I think your oil temp problem is coming from somewhere else. Are the stock lines and cooler optimal? No. But they are not causing your high oil temp/ bearing issues. Need to know what part number head gaskets. And take a close look at the raw water system on the boat from the drive all the way to the exhaust.

Originally Posted by ctuck0659

Long story of course but here's a summary: I had a very reputable performance engine builder rebuild my 502 rotating assemblies into 540's with Scat 1-42500 kits in 2013. He of course tanked the engines, spec'ed all the clearances, line-bored the cranks etc. Installed high flow oil pumps. All bearings and every internal engine part that moves was replaced. This is not a case of shortcuts taken or a shabby rebuild so please don't go there. . Originally used the stock remote oil lines, filter housing and cooler. After break-in switched to synthetic 20W-50 and started noticing oil temp went to 300+ deg after a hard run. Immediately swapped stock coolers to Revolution 3.5X18" coolers and oil temps normally ran 220 deg, never went above 260. This past summer I started noticing some loss in oil pressure so I did some research and swapped out the 3/8" oil lines for 12-AN. About a month after that both engines started to increasingly lose more oil pressure when hot. By the end of the summer the pressure dropped to less than 10 lbs at idle when hot so I pulled the engines and not surprisingly found severe bearing damage consistent with oil starvation. So the obvious conclusion might be that running the small stock diameter oil lines restricted the flow and is the cause of the bearing failure at less than 100 hrs. EXCEPT: how do you explain that the bypass valves in the block oil filter mount should have opened and shunted the oil directly back into the motors when the pressure differential got too high in the lines?? I change my oil approximately every 20-25 hours so there's no way there should have been enough normal combustion byproduct garbage in the unfiltered oil to trash the bearings after 90 hours. If the smaller oil lines are the culprit that's my fault and I can live with that, but I can't see how that was the cause given the fact that the bypass valves are engineered into these engines for that very reason. What I can't live with is not understanding what happened so I can make sure I don't make the same mistake again. Any thoughts or insights are appreciated-

Originally Posted by adk61

question for you..what is your system capacity? all this talk of temp, oil lines etc etc... no one asked the magic question, all the other things are relevant... but hi performance marine engines also need volume...