Re: 496 HO's- 425 at the crank or prop???
 

Don't give up on your stock manifolds, they can be modified.

Re: 496 HO's- 425 at the crank or prop???
 

Jim, for how much $ and for what gain and where? Worth doing to a stocker?

for lack of a CNC program, done by hand correct?

(BTW former CNC machinist here, B&S single spindle, Matsurra twins and Cincinati T-10's &20's...among others)

Re: 496 HO's- 425 at the crank or prop???
 

Black motors are RATED at the propshaft.

Blue motors are RATED at the crankshaft.

Example a HP 500 is RATED at 500 crankshaft hp and 470 propshaft hp.

I think what Raylar was trying to say is even though merc rates their motors this way the opposite seems to be true.

Black motors seem to have lower hp(a 496 being 425 at the crank) than merc rates them and the blue motors have more(HP525 having 545 at the crank)

Re: 496 HO's- 425 at the crank or prop???
 

either way- the thread served its purpose- I know what I really have and if I make mods to get some gains I'm better zero'd in on what to expect:)

Re: 496 HO's- 425 at the crank or prop???
 

An interesting observation...Merc used to advertise Prop Shaft HP for the 496 engines in all their literature, as they did on the 454/502 engines. Now if you read it, all reference to PSHP has been removed. Hmmmmm.

Re: 496 HO's- 425 at the crank or prop???
 

I've dyno'ed way to many 496HO's and I have the bills to prove it! I can tell you positively that 496HO's make right at 425HP at the crankshaft on calibrated dynos. Unless a Bravo uses 0 hp to get it to the prop, you are not going to see 425HP at the prop, more like 400HP at the prop. Mercury Racing HP525's make 525HP at the prop and about 540-550HP at the crankshaft. You can go the bank on these numbers!

Ray @ Raylar

Re: 496 HO's- 425 at the crank or prop???
 

Thanks Ray- good talking with you today :drink: