nsformula

I beleive the theory is that 496ho's will hold up with the standard whipple recommended kit
and 496mag's don't.
I say this after many years of reading Teague on Tech in Powerboat.
The question was asked many times.

CrownHawg

That don't make sense. You do realize the only difference between a Mag and HO are the cam and flash right? I recently had my two Mags converted to HOs, and for the most part it was a no brainer. Same internals in both motors. I have heard stories of 496s grenading after a whipple was installed, and other stories about folks getting 400-500 hours of worry free service with one. I have always been told, in order to "safely" mount a whipple on a 496, at the minimum, pistons and crank should be upgraded. I didn't have the $10K per motor it would take to "properly" install the whipple, so I went cheap and made mine HOs.

ZP'd

For the price and peace of mind why not sell the 496 stock and buy reliable blue power built to handle it.
A good used stock 496 is not that hard of sell. Mod em and your Customer base at time of selling the boat or engine shrinks.

nsformula

Here's a quote from Powerboat.
But you are correct, doesn't explain any difference in durability

ANSWER: The MerCruiser 496 Mag engines use a Hypereutectic piston, and always have. I would not describe the piston as "softer." Instead, I would refer to the piston as weaker and possibly more brittle than a forged piston. Any way you look at it, the piston is less tolerant to the effects of detonation.

What has changed are the crankshafts. The early 496 Mag HO engine models had a forged steel crankshaft while the non-HO Mags had a cast-iron crankshaft.

Now, for at least a couple of years, both models are equipped with the cast-iron crankshaft and the forged offering was discontinued. New crankshafts can't be purchased separately. You'll need to purchase a complete short-block assembly to get a crankshaft. So, the only differences between the two motors are the camshaft, ECU program and the throttle body.

Whipple Superchargers produces a kit for your motor that has good success. Included with the purchase price is the service of reprogramming the ECU for the new setup. This kit is especially good if you are using it to replace the power lost by running at higher altitudes. The 496 Mag HO is a better candidate for the Whipple Supercharger conversion for only one reason—the camshaft.

The "smaller" cam profile used in the non-HO Mag results in a less desirable higher cylinder pressure condition when used in combination with a forced-induction system. The good news is that all you have to do is replace the camshaft with the 496 Mag HO "bump stick" and you will end up with the exact same motor as a 496 Mag HO once the Whipple Supercharger kit is installed.

This is because the other two differences in the two motors (the ECU and throttle body) are changed when the Whipple Supercharger kit is installed. The ECU is reprogrammed and the throttle body is replaced by a Whipple throttle body. Everything from the intake manifold up (including the intake manifold) is replaced when the Whipple kit is installed.

Indy

Agree. I wouldn't get near one if they were in a boat I was looking at.

CrownHawg

When you look at my boat, you would never know the motors started out as Mags. Even have the HO engine covers. Totally stock!

Baja_man

I've seen my fair share of blue motors having equal problems. Regardless of which base you use, 496 or 502, I would suggest doing it right the first time and be worry free. There is no cheap HP and speed to be had.

mikebrls

from what I have read the 496 ho with supercharger can live a long time But you have to baby the motor . In other word's No wide open throttle for any amount of time ." ok maybe one minute or 2 and that's it .
I think if you run the boat at mid range to pick up a better cruise speed they work fine but if your going to be Jo racer and jump wave's and do whole shot's they won't hold up as long

mike

JBoat

how much hp are you looking to gain ? Tyler Crockett has made mine at 585 hp with out running any boost at all. Cam, ported head and a new ECM map has added a safe 160 HP without the worries of what boost will do. Just another idea to consider

CrownHawg

Wow! That's quite a bit of hp. What is your rev limiter set to? Do you have to run 93? That sounds pretty good!