LA3

OK, someone help me.
How many combinations of 502's did they make.
MPI? EFI? MPI/EFI?
Or all they the same.

I understand that the MPI and EFI are different and
that some super chargers and aftermarket thing will
not bolt on to both.

Which engine is more reliable and easier to upgrade?

What are the fundmental differences?

Thanks in advance

mjb

Mercruiser makes the 502MPI, black motors rated at 415shaft/435 crank HP.
Mercury racing makes the HP500EFI, blue motor which is a 502 rated at 470shaft/500 crank HP.
For the most part, the short blocks are the same but most of the top end, fuel injection etc... is different.

LA3

I am just looking for the BLACK motor types.
I have seen 502 MPI and 502 MPI/EFI.
Is MPI and EFI the same thing?

Again, which one is better for performance?
More reliable.

Thanks

HiPerf2000

Mine say EFI / MP on the plenum.

I always wondered what that meant myself.

hillbilly24

EFI=electronic fuel injection, I hope you knew that one MP=multi port later change to MPI wich is multi port injection.

articfriends

I think what your asking is the difference between the early 90's and late 99-2000's. They are both multiport and both "batch fire " which means they fire 1/2 of the injectors on one revolution and the other 1/2 on the next revolution. The earlier ones were gen v blocks and later ones were gen 6 blocks. They both have the same basic steel cranks,forged pistons,7/16 rods etc. The real difference is the early ones had a different fuel regulator and vst,later ones had a better fuel cooler called "cool fuel" with shorter injectors and a mefi3 computer. From what i know the newer ones have 43 lb injectors and vst models 38 lb injectors so it is really minor difference's between the fuel injection systems,Smitty

articfriends

Which engine is more reliable and easier to upgrade?

What are the fundmental differences?

Thanks in advance[/QUOTE]
The cool fuel models(98-99-2000)have the mefi3 and are best ones to modify as far as superchargers but older ones can still be modified too,Smitty

LA3

Smitty,

Thanks a mil.

Now what can I do to upgrade. Simple bolt on or switch out stuff to gain some hp.

Do they make chip or something.
I know you can do exhaust, props, etc.
Looking for some other things.

Engines have OK serial numbers. Which merc says were built in 97. Gen VI.

502 MAG MPI (GEN VI) GM 502 8 1996-1997 OF802600-OK999999

502 MAG MPI (GEN VI) GM 502 8 1998 OL017000-OL085432

502 MAG MPI (GEN VI) GM 502 8 1999 & up OL085433-OM024999

Is mine the one with mefi3?

Thank you so much. I have lots to learn in short time.
LA

East Coast B

I'm not familiar with the various 502's, but am familiar with the smaller engines and mercruisers naming conventions carb vs efi vs mpi. Carb and mpi are pretty straight forward, however the efi versions were nothing more than a throttle body setup. I know the 502 early edition carb was 390hp I believe and the mpi 415, so my question is if the 502 ever had an EFI designation with the throttlebody setup???

DORaymond

Do the current MPI motors "batch" fire. Sound pretty inefficient to fire half of the injectors at the same time(?). What happens to all that extra fuel?

Don