I have a 1995 Formula 252 with 454 Mag EFI Gen VI. I am restoring it. Motor has low hours (237). Looking at possible exhaust manifold upgrades. Currently has Merc Manifolds and Risers. What recommendations do you have for new or used parts. Are Stainless Steel or Alum worth it? Boat is raw water cooled and would be used in fresh and brackish water. Exhaust is thru prop, nothing special.

As a side note I will be adding a whipple performance tune at some point once I am done with the major work. Supposedly that is 425hp and 5400rpm. I need the power for 6000ft Lake Tahoe running.

The mag has 385hp. Whipple will put you way over 425hp.

No thru hull exhaust?

I upgraded my 454 manifolds to modified aluminum 496 manifolds. Even the cast iron ones would work well for you. and alot cheaper then aftermarket manifolds

Not without a supercharger.

My question with the EFI tune , is 40hp gain for real ? I don’t get it but I don’t get much. Anyone verify ?

I had a 454 MAG EFI upgraded by Tyler Crockett years ago. Upgraded cam, head work, exhaust (Stainless Marine Manifolds) and tune. The engine

dynoed at 461HP. It really woke the motor up and sound difference was incredible!