I'm swapping a late model (2003) 8.1l truck engine for the stock 7.4l mercruiser in my 1990 baja. I'm wondering if I can use the stock GM ECU, and if I will need to re program it. I'm also wondering what I will have to do to deal with the change in exhaust from stock truck exhaust manifolds with oxy, and other sensor take-offs, to my water jacketed boat manifolds. I know that the oxy sensor is one problem and there is also another port on the truck manifold that I will not have on my boat manifolds. I would appreciate any insight into this swap because I am starting from scratch on this, and I need some help.

 

I don't think anybody makes the tuning software for the Mercruiser ECU's. You might call Mercruiser and see if they have a way to reprogram it. As far as the rest of the stuff for the swap, I really don't know.

 

Your marine exhaust manifolds will fit the 8.1.

There is tuning software for the MEFI ECU.

Since your boat doesnt have an O2 sensor, your 8.1 wont need one.

Do a google search on MEFI tuning, you will find tuning products. Whipple also tunes these ECM's.

peace
Hog

 

Hog, do you know where i can get ahold of a mercruiser mpi intake for my 1997 chevy 350 for i decent price, i have looked alot and i cant seem to find one thanks chase

 

You might need to run spacers on the manifolds for the 496.. They some times will hit the valve covers.. Also asm/Tyler Crokett can do a computer reflash on your marine ecu. Some marine ecu's for mpi set ups can not be reflashed.. I also have a COMPLETE throttle body /computer set up. Would allow ya to run a hot rod intake manifold.. MPI set ups are going to run you well into the 5-700 range, depending on what all your getting with the mpi... PM me if your interested in the TB set up..

 

You are right about the intake spacers as teh GEN VII 8.1 is a tall deck block.

peace
Hog

 

Michigan Motorz sells them brand new for $799.
5.7L & 5.0L MPI Cast Iron Marine Intake (2002-2009)

Parted out at Mercs prices theres over $3500 of parts in that setup.

peace
Hog

 

check out this vortec headed marine intake

Mercruiser 350 Magnum Intake Manifold / Fuel Injector - eBay (item 300572835992 end time Oct-01-11 23:40:39 PDT)

Raylar would probably be your best bet on your retrofit. I dont particularly like the guy but i am sure he would know the most about it. My truck used to run on a marine pcm and yes software is available

I also went from a marine 454 to a 496 into my truck.