Current boat is a 1998 Velocity 26/28 with a 502 mag mpi, (MEFI 1). When the motor needs to be freshened I could keep it a stock 502 cu or punch it out to 540 cu. I have an HP500 EFI intake and TPIS TB. I also bough a MEFI 3 ECU and wiring harness for a 502 MPI.
I plan to run HP500 iron heads or just have the larger valves put in my stock heads and a stock HP500 cam or custom cam.

So my question is since the motor is and will be NA, should i just stay with MEFI 1 MCM or should i go ahead and upgrade and use the MEFI 3 MCM?

r,

Eric

MEFI 1 is the simplest but lacks tuning fidelity in the fuel tables. Not a deal breaker and the motor likely won’t know the difference. MEFI 3 takes longer to load and is a little more complex. If you are doing the tuning the MEFI 1 is an easier starting point. Just size the injectors appropriately and dial in the fuel table. Then work on the timing table. Most other tables don’t need touching.

If you use the 500 intake, swap the injectors for 48 lbs if your tuning it yourself, if you simply put either ecm on the 500 intake with stock injectors without rewriting the tune in ecm, it will be so lean it will hurt the engine the first time you lean on throttle and stay in it (that is if it isnt lean popping so bad it scares you). . A 500 efi uses 33% smaller injectors then a 454/502 mag and neither the gen 5 honda keihan injectors nor the Maghetti marrelli gen 6 will directly fit a 500 intake. Surprisingly the 525 uses same exact injectors as a gen V 454/502. If you need tuning help and dont have someone locally who can help, pm me, Smitty