I am looking at a '99 Velocity 320 with T-454 MPI. They are completely stock other then Stainless Marine exhaust upgrade. Are these the 454's with the forged crank and rods or is this cast junk? Are the MPI's best left as MPI's or would a carb upgrade be valuable?

Is there a 454mpi and a 7.4mpi that are two different beast. I know from what I've read here that the 7.4mpi is crap for upgrades and not much horsepower (310), but that it will also last twice as long before rebuild.

They have forged internals.

The engines will be labled as 454 Magnum MPI's or 7.4 MPI's. You need to find out which or find out which HP they are to determine the answer to your question.

They are 454 MPI's.

I guessing you are talking about this boat.

http://www.offshoreonlyclassifieds.c...o17643-en.html

He can call them whatever he wants. If they are not a 454mag MPI's then they are the 7.4 mpi's. Post a pic. BTW if they are not mags, then the internals are cast.

Here's a list of merc sterndrive engines. Nothing is labeled as a 454MPI.
http://www.mercruiserparts.com/selec....asp?type_id=8

I would go with what Griff Says. No matter what the engines do say on them, if they don't say "MAG" or "MAGNUM", then you can bet they won't have forged internals and aren't useful for doing bigger horsepower upgrades.

That would be the boat. I will get some numbers off the motors and we'll know for sure.

Here's another example of somebody calling their engines 454 MPI's. Sure they are 454ci, but they are 7.4MPI's as shown in the pic. They have the weaker/cast internals and 310hp.
http://www.offshoreonlyclassifieds.c...o18159-en.html

These are true 454mag MPI's with forged internals and 385hp.
http://www.offshoreonlyclassifieds.c...o15828-en.html