Last year I took everyones advice and built a nice 540 for my Powerquest. The only thing I didn't address was the oil cooling system at all, other then a Melling 10778 oil pump and a 10qt pan. After reading thru numerous post and articfriends oil pressure hardware thread I dug into the system from the factory 502. What I discovered is my oil cooler is 3x20 and my lines after removing them all have a 1/2 ID. So now im a little confused, alot of people post about upgrading there Gen V and VI stuff from 2x18 to 3x18 and from 3/8 lines to 1/2 or 5/8. So with my cooler and lines being decent size am I able to keep the the cooler and lines I have, or should I replace my line with -12AN which should be 5/8 ID. Just seeing what people think, or others have done. Thanks

the gen 4 seems to run hotter oil temps, I ended up with Teague's offshore oil cooler. I still see higher temps than I would like on extended WOT runs. #12 lines swept elbows, remote filter drilled out internally, plugged bypass in remote adapter. The motor is still running well after 10 years.

What HP is the 540 making ? I don't really see an issue with the lines and cooler you have if there is no 3/8 ID bend's in any of the fittings.

OK, do you know what size your stock cooler was and then the size you upgraded to by chance?? And I definitely like the idea of larger lines so far and try to eliminate and 90 degree elbows. Unfortunately last year I ran stock gauges and never had an oil temp sensor, new gauges is on the list. I figure while the motor is out of the boat this winter I want to address any issues while its tore down.

It should be in the 650 range I would imagine. I never had it on a dyno'd but im running 9.1:1 compression. Canfield 119cc heads, currently be lightly worked over by Jim V. Crane 741 cam with a Merlin intake and Quick Fuel 1050 with lightning headers. I was hoping I could atleast reuse the cooler being that it is 3" already. Its just hard to find Mark IV info. Everything ive read says to switch to a 3" I just have no idea how good the stock 3x20 is and if it was normal to be put on the 502's as well.

went from 2x12 to the offshore cooler, water temps get very warm down here, did not want to take chance, 600hp N/A dyno verified

A Whippled Merc 525 runs on a stock cooler and lines and makes in the 800hp range........

OK awesome. What size cooler comes an a 525 I hear alot of guys upgrading to the 500 or 525 cooling systems for a budget way to go.

Are you sure its getting to hot, have a gauge on it?

I think its a 3x18 or 20...here's one