Merc HP500 Exhaust
 

I am looking to swap my gen V 454mag with 600 hours for a rebuilt merc 500hp from a local marine mechanic with a solid reputation. The engine comes without exhaust and we talked about either A.) Keeping the 454 mag exhaust setup with corsa silent choice or B.) buying a set of new or used cmi headers. Buying new exhaust will be better but it will also run a few thousand dollars that I dont have right now. Can I keep the stock 454 mag exhaust on this engine and buy headers after a season or two? I posted the engine build info below. Thanks.

Bored .030 over, from 502 c.i.d. to current 509 c.i.d
589 Dyno proven horsepower @ 5600 R.P.M
*Engine is completely rebuilt, all machine shop work and rotating assembly work performed by K-S Machine Shop.
-Cylinders bored & honed.
-New cam bearings.
-New crank bearings.
-Balance Crankshaft.
-New roller lifters/rockers.
-New ARP rod bolts.
-New JE pistons.
-7/16” Bolt forged rods.
-Crane cam/Keith Eickert camshaft

I guess not

Hp500 cam with 454 mag manifolds? You're gonna revert water. Not a good idea using those iron manifolds with a 110LSA cam.

The stock cam was replaced, although I am not sure of the specific LSA or lift. When I talked to the builder last he said it is specifcly cam'ed so there is no overlap to avoid reversion. If this is true can keeping the iron manifolds alone lead to water reversion?

with a stock type manifold like that ,it will hurt you in two ways.like mildthunder said.they will " drink water" and will not flow well.a cheaper choise would be a stainless marine manifold set up.this system will outlast headers hands down and will almost flow as well as headers.

Post the cam specs if you can.

ok thanks for advice guys

I have a set of mint low hour freshwater use only cmi headers with bravo tails email me if interested
I can make a pretty good deal on them.
[email protected]

No way an HP500 bumped to 589hp will be able run 454 mag stock exhaust and not revert water.

I thought the HP 500 came from the factory with the Gil manifolds? Is that incorrect?