cableguy1979

Some of you may remember my situation. I have a 1996 Crownline 225 CCR that had the 454 MAG MPI gen v engine. It spun a bearing and cracked the block and I was going to rebuild the engine but came across some 502 Mag MPI gen vi engines. I have the engine ready but my question is about remapping the ECM. I have done some research and found that Whipple can retune the computer to a 502 increasing the advancement and rev limiter but I have to use 91 or better octane and at the cost of $600. All i really want to do at this point is simply remap it to a 502 mag MPI setup. I called the local Mercury dealer and they say they cant do it anymore. Does anyone know anyone that can do this as it should be a simple $100 remapping? I have another 502 I'll build and then remap but I want to get back on the water pretty quickly.

cableguy1979

The next question is the Gen V has a MEFI 1 ECM but the engine is a Gen vi which I believe came with the MEFI 3 ECM. However I believe the 502 MAG MPI was also offered in Gen V the only difference being roller rockers? So I guess my real question can I get the same tune as the Gen Vi to work on the MEFI1 ECM or will a Gen V 502 remap on the MEFI 1 ECM work for the Gen vi motor.

Trash

I am assuming you are using the 454 ecm and intend to use that on the 502s. Get the motors assembled, wired and plumbed and run them on a test stand (preferably) or in the boat utilizing the existing ECM tune. The motor will start and run and do so safely at idle and no load with the original 454 tune. You would need to have wide band O2 installed to see what the AFRs are prior to doing more tuning. Your best option is to get MEFI Burn and dial the motor in yourself. You will not need many changes or as much as you might anticipate.

It is NOT difficult and you would mostly make minor adjustments to the fuel and spark tables.

Trash

The motor does not care what version MEFI is running it nor does the MEFI version care what motor it sits upon. The motor only wants to see correct fuel and spark. If you have a a MEFI 1 with a 454 tune use it on the 502 as I stated before. The MEFI 1 is very simple and easy to work with, but lacks the fidelity of later MEFI units, or any other later ECM platform. For a basic N/A motor the MEFI 1 is fine. MEFI 3 has more fidelity but also takes much longer to load the tune.

A MEFI 1 tune will not load on MEFI 3 and a MEFI 3 load will not load on a MEFI 1.

IF I was you, I would use the MEFI 1 and tune it myself.

Trash

I don't believe any of the 454 or 502 black motors came with roller rockers. They would not affect the tune at all assuming the same ratio.

BUP

iTrader: (9)

throw a custom carb and high rise performance intake on it and call it a day. Also install current fuel delivery system set up and call that a day. How long will the mefi 1 last and if you have the VST set up that is on borrowed time as well. Prob doing these installs you can get closer to 1 hp per .

cableguy1979

Thanks for the input guys but I plan on keeping the fuel injection and I really dont want to tune the engine myself since I dont have the software and I dont know what Im doing. For $400 Arizona Speed says they can put the 502 tune on the 454 ECM MEFI1 computer but will it work? A intake and carb and or software all cost more money then just reflashing the computer if it is possible. It seems to me this should be a easy thing to remap to a stock 502 EFi tune as Im sure this motor was also offered in GenV. It has the exact same heads, intake, crank, rods, and so on. Surely they made a VST 502 motor. Im not looking for top end or performance. Im simply trying to get back to the water.

cableguy1979

That being said I dont know if the roller cam in this motor is actually any different and could change how the tune operates.

Trash

The MEFI 1 will be fine. It is simple and robust. I have over 25 years of use on mine and 100's of tune installs. VST can be rigged with fuel return to tank and a new internal gasket kit if needed.

Trash

It is an easy thing to reflash the MEFI 1 to a 502 tune. You will spend $400 for AZSM to reflash the ecm or you can spend $600 and get the software and do it yourself. IT IS EASY! Plus you can tailor the tunes as much as you want on your time frame. I would run the motor on the existing tune FIRST then reflash/tune as necessary.