Been studing an article in F&P Boating magazine on the up-grades of 7.4 L pre-1996 carbed. . Anyway minor changes included, Heads from a 1997 or later, cam shaft change, exhaust etc. This engine with these mimor changes can get you upward of 425-450 hp.
My Baja is a 97 with the L-29 Vortec heads. I wrote the author asking him if a set-up similar to this would work for my 7.4 MPI . He recommended:

I already have the required heads

Comp Cam 218 degree intake and 224 degree exhaust duration with 112 lobe seperation

Increase my fuel pressure a little with a new fuel pressure regulator

And of course, exhaust ( he recommended Gil exhaust)
He said this would get me in the 425 hp range.

Does it make sense to you guys
Except for the new exhaust, this seems like a fairly in-expensive way to gain some added hp. Opinions please

I don't have any numbers for proof, but that sounds like a huge gain from basically just a cam and exhaust swap.

here is the email I got from him, I think its possible but tou have to tweak the fuel presure to get the mixture just a hair on the rich side...


Russ, the 330 horsepower is measured at the crankshaft, if it was measured
at the propshaft it would be 300 horsepower. Your engine is measured at the
propshaft, 310 horsepower, if your engine was measured at the crankshaft it
would be 340 horsepower. You have one of the best marine engines built, I
really like the cylinder heads and the fuel injection unit. The only
modification I would make to your engine would be the addition of a Gil
exhaust system and remove your camshaft and send it to Comp Cams and have it
reground (much cheaper than buying a new cam) to 212 degrees intake duration
and 218 degrees exhaust duration with a 112 or 113 degree lobe separation
angle (keep as close to the stock valve lift as possible). Call the Comp
Cams 800 number for advice. Install a fuel pressure regulator that will
increase your fuel rail pressure (it is located on the Mercruiser cool
fuel). Changing to an intake manifold and carburetor is the only way to
increase horsepower past 400 without having to mess with the computer. I
have a book I have written called BIG BLOCK CHEVY MARINE PERFORMANCE that I
can sell you for $19.95 ($17.95 + $2.00 ship) send a check to Moore
Performance, PO Box 1413 Monrovia, California 91017 (write BB Chevy Book
on the check and include your phone number)

Russ, what year engine do you have now" is it carbed?? I'm a little confused with Dennis' quote. He told me the same thing and I have an MPI

I don't get it.... Your first post says that with minor changes, exhaust, cam, pressure regulator you can get 425-450 hp. Your last post says that you have to change to carb. to get past 400 hp.

I am not breaking your balls, I am just confused as to what he told you. I too would love to increase power in my 454 Magnum, but I am afraid of the re-mapping of the ecu. I have heard of too many engine blow-ups after supposed "experienced and qualified" people have re-mapped ecu's for some of OSOs' board.

I dont know squat about efi or computer motors..and I'll be the 1st one to say it, thats why I dont have one....but 425-450 hp is easy to get out of a carbed 454 motor.
My feeling is the efi puter motors are great for starting, milage, emissions, etc, but if someone monkeys with the puter..its a crap shoot and you can only hope hes got it right. Too many fools out there think they do.
Dennis Moore knows his ****!!

Dan
I just re read the posts
It sounds like efi needs a puter fix to make 400hp and up
I guess if you put a carb on it you throw away the puter and will make over 400hp. The combo he described sounds about right for that hp.

I have a 99 7.4 l mpi (310) it still has the mpi on it I was thinking of swapping it out with an aftermarket intake and carb for more power and also being able to jet it, when someone reprograms the ecu the main thing that happens is the injector is told to let more fuel in, you can do the same thing with an adjustible regulator. by increasing the fuel pressure. when the fuel injector opens it pumps in more gas which will be needed because the engine is pumping more air from the cam and exhaust(the engine will be lean and you need to richen it up. if its not the changes did nothing). the problem with some of the re mapping is if it goes lean after you get the ecu back then you have a real mess you have to learn how to read plugs to do this correctly even if someone else does it for you.

It had me a little confused too, so I ordered his book.