I am in the process of purchasing a 502 mpi mag that has low oil pressure. didn't knock or anything just ran low pressure.
my questions are what can I do to stay Fuel Injected. What canI do to modify this engine in the rebuild process to run stock computer with out tuning to make more power.
I have heard that I can mill block and heads to bump compression, and a few other things to get this engine to make more power.
I plan to do a cam once I have exhaust and other stuff, so more than likely next summer. I would like to make 500hp with this engine. 2000 502 mpi mag. is this possible?
I just don't want to have it tuned by ecu. until I have a cam and other stuff like heads and what not. this summer heads and stuff isn't a option. just want to do that stuff at one time. I just want to squeeze what I can out of it the way it is with machine work and springs, rocker arms and what ever else to make this possible. I plan to disassemble the engine and rebuild it before it goes back in boat. if anyone has any experience with this lmk. im headed to bed had a few 100 to many tonight but would like to start planning, thanks in advance...

From what I've read on here you can't do much without remapping the ecu or you will be rebuiling the engine very soon, your better to either stay stock or bite the bullit and do it once. Or you can buy an after market programmable ecu to squeeze the most power from your mods

It depends on which ECU you have.
Or search the swamp shop or classifieds for a complete takeoff. This link is for 525 EFI setups.
http://www.offshoreonly.com/forums/s...on-system.html

I remember seeing this subject covered over a couple of issues of hot boat magazine when the 502efi came out.dyno testing and all . If your going to open it and the crank is damaged ,might want to look at a 540 kit .

Yeah thats next year, I wantbto accumate the parts and do it all at once. As far as right now. I just planned on doing the "FREE MODS" like milling heads and just getting power out of all the hidden areas. If they exist

This is just one 502 owner's opinion- don't touch it your first year.

You have no baseline for how that engine performs, you'll never know if your mods have been a pro or con. You think that engine has low oil pressure, or maybe the hull it now resides in has a bad gauge?

Fix what you must to make it sea worthy, then just drive it. You'll learn its quirks, like how much oil it consumes, what temp it holds, maybe it vapor-locks, etc, and these are important to how you plan your build.

I asked about the gauge just a bit ago and the response that I got was, the mechanic diagnosed the engine to have low pressure, and ruled the gauge out. basically.
Now the guy that I am buying the engine from seems to be very honest, I do like the advise of just put it in stock and see how it runs. supposedly my boat with a stock 502 runs 70mph with a 28p from the factory. so really I don't need anything else this year. Since there is no way to directly point at what could be wrong with this engine, at the very least Ill pull it apart have block checked, re ring It, new cam bearings, new bearings, and slap it back together. I just didn't know if I milled heads and block if that would effect the tune, or if putting nice springs in the heads would help or effect tune.

what is the low oil pressure# on a mechanical gauge?

i highly recomend a valve job with new valve springs while the heads are off,it,s well spent money imo.

not sure if it was checked