What kinda boat is this going in, its one thing to drive around at 75 or 80 mph doing a tune vs 100+? The problem with tuning on the water with something that is on the edge is its hard to get "clean" safe water and do wot runs to tune things in safely . A self tuning ecu like Haxby is talking about would be a big plus for what you want to do but not a absolute neccesity. I feel bigger hp blown motors should be tuned on the dyno as there is so much going on when your boosting something and so many variables that how would you know for sure that your making max hp while dodging things in the water at 100 + mph and keep in mind if motor goes lean under boost and you don't catch it fast enough it doesn't take long to turn pistons into Souvenirs (they make great ashtrays for your buddys that smoke), Smitty

Post the part number off your ecu and we will tell you what it is, Smitty

If the ecm is square (about 3" x 3") and has the plugs going into the top of it and has the 8 digit # ending in 099 or 999 it is a Mefi 3.
Eddie

This setup is in a 04 26 American Offshore. Eddie I dont have my ECU mith me, Im waiting for it to come back from ASM but I think it is the Mefi 3. The pluggs are on top like you said. The boat will run 98 with a 30 pitch labed 4 blade and only making 2lbs boost @ 5400 rpms. Im planning on setting it at 8 lbs then doing some prop work. It never was tuned or the correct prop to begin with. Im sure ill end up going to a diffrent outdrive from the bravo xr and IMCO lower with 1.5 gears. My goal is to break 100 on a conservative tune. Bob I might give you a shout when I can get off this turnaround...

I also live in Beaumont, have you talked to any of the guys with powerboats there ? do you know George ,, Ronald or Regan ,, Mark ,, B.J. ? George gave me a couple of names, Crocket Marine in Ruby, MI. 810-324-2720 ,, Precision Marine in Kenner, LA. (504) 469-7463 ,, Full Throttle Marine in Spicewood TX. (830) 693-5591. I've spoken with all three several times. i'm taking mine to Full Throttle because Crocket is just to far and Precision mainly deals with Big Blocks. I'm going from 350MPI to 383MPI with several changes
. i am getting them dyno. i also have MEFI 3,,,

,,

sorry for last post guys ,, went to wrong post

I also live in Beaumont, have you talked to any of the guys with powerboats there ? do you know George ,, Ronald or Regan ,, Mark ,, B.J. ? George gave me a couple of names, Crocket Marine in Ruby, MI. 810-324-2720 ,, Precision Marine in Kenner, LA. (504) 469-7463 ,, Full Throttle Marine in Spicewood TX. (830) 693-5591. I've spoken with all three several times. i'm taking mine to Full Throttle because Crocket is just to far and Precision mainly deals with Big Blocks. I'm going from 350MPI to 383MPI with several changes
. i am getting them dyno. i also have MEFI 3,,,

without wanting to piss anybody off...I would get rid of all the merc junk...worthless for what you are trying to do...to many good EFI systems out there now that you can tune...unlike the merc junk..