I'm going to rebuild a 502 415 horse Merc, and I'm considering taking the MPI (EFI) unit off and replacing with a carb, what would the system be worth?? It's a 1999 and in excellent shape, approximately 80 hours on it.
Thanks,
Bob G.

Bob, why would you do that? Seems like a step backward.

Michael

Good question actually.
The Merc EFI stuff is run open loop, meaning that if you change something, the EFI will have no idea about that.

I assume that Robert wants to upgrade his motor/s, so what does that leave you? You are up against a programmers' wall at that point. Today, carbs are still the best way out of that problem. It would be insteresting to know how many motors were toasted by improper programming.

What I should do is figure out a way to make a fully programmable Merc EFI computer replacement.... It could be done, but would be an effort. Humm...
Kent

I'm considering upgrading the valve train and cam-looking for more horspower. I believe the pistons/crank are the same as an HP 500. I have an intake and carb, but was told the MPI system would "get confused" and would not work. I am not a mechanic, I'm just going by what I've been told. I'd like to get around 475 horsepower to run a P5 boat. Any suggestions??
Thanks for your responses!
Bob G.

475 horse w/ the 502 mpi system is not a problem. Quite a few shops have proven setups w/ upgrading 502mpi engines and are getting more horsepower than that. I have been told that 530-540 horse is about it with that system and requires quite a bit of messing around. I have 2000 502efi's that were upgraded by Lingenfelter Performance and they claim 540 horse on the dyno. They idle and run very nice and still have all the nice benefits of efi.

Thanks for the info BGIII

Robert we can set you up with the right parts to bring you up to 500Hp and we will program your ECU for you. Tyler

You can't go wrong with Tyler Crocket marine, he has in house dyno's and a full machine shop, he can also mapp your computer to work with a proven dyno package

WOuld that system be worth a trade for an HP500 Manifold and carb with air cleaner????? Money for money i mena?