Offshoreonly.com - ZT-280 454mag TOP SPEED?

Quote:

Originally Posted by zt260

Merc calls the 496HO 425HP propshaft. The 454mag was rated several ways, but I believe the 385HP model was at the crank so subtract ~30HP for propshaft. Either way I'd still say the 454mag will only hit low 60's in a ZT280.

I don't know anything about the 496ho but i can tell you that the 454 mag and 502 mag longblocks are off the shelf gm H.O crate motors with no internal differences except smaller cams from what gm used to sell. From gm they are rated at 450hp/425hp respective to their sizes. A 454ho usually makes 435-438hp on dyno with headers and carb,Smitty