Has anyone had good luck adding prochargers to a boat with MEFI 1 for the computer system. I have a 1997 29 Fountain with 454 mags. I just added m1 prochargers to it and want to try to run it safely without having to change the entire wire harness and computer system. It has the ATI regulators on it now, so I'm assuming I need to change those to better ones at a 1:1 ratio maybe?

Thanks for any guidance,

Zack

Its definately the worst mefi for running boost, no map table past 100kpa, the fuel tables have huge jumps in them and no timing reduction table for boost. The best you can do is add a bunch of fuel at 100 map and boost reference the regulator. Its a very crude way to do it and wont be tuned real great when done. Personally i would swap ecus and harnesses or repin the harnesses (ive never personally repinned a mefi harness that worked when i was done but the only one i did was from mefi3 to 4 after crockett told me it works then when it didnt he said it was better to just get a new one).

Thanks for the reply. I talked with Precision Marine and he kind of told me the same thing, he said with the M1 and 5lbs of boost he can make it work by adjusting cold fuel enrichment and adding fuel up top, plus a working regulator. I have one regulator not adding fuel with boost, so I need to change that. I pulled the ECM's last night and they had stickers on the from Precision Marine, so I'm assuming he already did the work for this boat. I bought it without prochargers, but I could tell it had them previously by some of the parts they left on it. I'm planning on adding 02 bungs to the risers so I can read the A/F and giving it a shot.

I will echo what Artic says. If all I had was a MEFI 1 and doing a N/A motor I'd keep the MEFI. If I had to do boost a MEFI 1 is problematic for all the reasons mentioned. It can be done but is difficult and crude. I'm just not a fan of using fuel pressure to alter AFRs.

Back before the Dinosaurs existed, Procharged designed a fuel system for the MEFI 1's. Right after the dinosaurs died I installed and ran a MEFI 1 Procharger system. What a joke. Sadly, they still use the same system.

Listen to ArcticFriend's. He's been elbow deepin this stuff for seeming forever too.

Yeah, I have learned a bunch in a short time. I did not know that I was going to have a computer issue before I put them on. I'm trying to make it work with what I have. If I can't, I think I would just pull them off before I changed over both harnesses and still have to have that one tuned.

I had the same problem running a MEFI1 on a Procharged engine. Added an O2 sensor to find out I could not get a decent fuel curve by jacking up the fuel pressure. I swapped out the MEFI for a Holley HP controller which was pretty easy only had to splice 5 or 6 wires everything else plugged right in. You can control all engine parameters with the Holley and run in closed loop with an O2 sensor. Holley HP was about $1100 and then you need to add an O2 sensor bung to your exhaust. Times 2 for twin engine boat.

So was that the Holley ECU and a whole new harness? Then did you tune it yourself? Did that make it a lot better?

To be blunt, a procharger setup on a stock merc EFI engine is like pull-and-pray....all they do is jack the fuel pressure into the twilight zone and hope it lives...

I purchased the Holley from Alex Haxby on here. He loaded the base tune to get me started. The Holley made everything better as I can create a timing versus boost map, Hook up my knock sensor, Program fail safes for low oil pressure, fuel pressure etc. The Holley will fine tune the fuel curve to the AFR,s you specify using feedback from the O2 sensor.

The harness is included. Plugs right into all your sensors, distributor, and injectors. You will have to splice a wire for fuel pump, 1 for distributor, 1 for 12 volt switched power, 1 to an engine ground, and a positive and negative direct to the battery. I was able to figure it out and I am just a dumb carpenter. Basically the only thing left of the original harness is the cannon plug and the main breaker.

I used this with an Aeromotive regulator instead of the ATI regulator. The Aeromotive is a 1 :1 regulator and is very consistent unlike the ATI.

I believe you can get by with the stock injectors at 5 pounds boost.

Search some of Eddie Young"s posts on here concerning Prochargers he gives out a lot of good info.

If you are mechanically inclined and like working on your boat as much as driving it you will be happy.

If you are just looking for a bolt on and go I would take it to a professional which is a whole new subject as to who to trust.