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

New to the engines- just trying to read up and figure out what tweaks I want to do down the road (leaning towards CMI's).

Are these 425 at the prop? Somehow I had it in my head the black motors were prop rated.....

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

425hp @ the prop.

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

Yep, 425 at the prop. Add approximately 30hp to get crank hp.

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

The 425 hp is at the CRANKSHAFT.

My 25 Outlaw did 67 mph (@4900) last year with the stock 496HO motor. This year it does 80 mph (@5300) with a HP525EFI and extension box (GPS best was 81.2) Let the box account for 4 mph. Then we are down to 76 mph from the 525 (which is pretty close to what Baja claims for this combination). That´s still a 10 mph gain from 100 hp (which just isn´t possible).

The 525 does produce 525 prop hp and the 496 produces about 130 hp less. Then the numbers start to make sense.
.....or the 525 produces EVEN more than its 525 hp, which wouldn´t make sense either!

On the Merc stand at the Miami Show this year, the only motor where PROPSHAFT was quoted next to the horsepower rating on the spec. boards, was the 525.

The 496 is a terrific motor, but its power curve levels off at around 4800 where the blue motors just continue to climb.

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

425 hp is CRANK hp as proved by Raylar, Tyler Crockett, Dustin Whipple, etc., etc, etc....

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

Fair enough, fwiw the 525's are known to dyno at 540/560 at the crank all day long.

I was looking through old mags, it looks like Dustin had a stage 3 kit which was dropped (na kit).

From what I'm seeing- labor and cash it's hard to beat the CMI's. AS&M has a nice intake kit but so far they have not confirmed what it makes with stock exhaust vs dyno headers or if it still uses 87 octane. The Raylar packages are nice but I can't justify the combined expense on low hr engines- anyhting else out there? :D

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

25 outlaw, stock 496 HO, 67 mph? Mabe on the trailer.

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

You don't want to start with Wild Card 09, go over to TBM and search and look at his project he has been doing, more importantly, his quality of work.

He knows his $hit, trust me.

BTW, I have a 1995 272 502mag (415hp) w/ labbed 24 67MPH GPS. I am in the process of adding some Etops, hope to hit 70.

Chris

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

Just to clear the deck here and put in some facts. All Mercruiser engines are rated by SAE standards at the crankshaft. Most all dyno tests of the stock 496HO including ours show the engine produces approximatley 425HP at the crankshaft as advertised. Mercury Racing engines such as the HP525 are rated at the propshaft. The Merc HP525 when measured on a dyno is at about 540-550HP at the crankshaft.
Our 496 -525HP kit is rated 525HP at the crankshaft with stock exhaust. When equipped with a good set of headers, it also produces about 550HP minimum at the crankshaft at 5100 rpms. Just some facts to avoid mis-information here.

Ray @ Raylar

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

OK...now I'm really confused. Everything I've read is the opposite of this, but I just searched the Mercury Marine website and couldn't substantiate it either way. Trust me, Ray would know a million times more about this than me, but I thought the oppostite of this was true.

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: