Making the switch from 454 to 496 ho
 

I am getting ready to make the switch from a 1999 454 mag 310 hp. to a 2004 496 ho. The boat is a 1999 Baja 272. I have a couple of questions about the install. The 454 is raw water cooled and has silent choice. The 496 is fresh water cooled and straight exhaust.

1. Can I add a wye/ down pipe to add silent choice and if so will the silent choice for my 454 work on the new 496? I would like to be able to keep it quite around the marina.

2. Since the 454 is raw water cooled and the 496 fresh water cooled do I need to do any thing with the water intake?

3. With a 115 hp difference what kind of prop change will I have to do? I am currently running a 3 blade 23 pitch ss prop.

Thanks for the help!
Lt.

Re: Making the switch from 454 to 496 ho
 

Please check around with builders and dealers who run performance boats about the longevity of the 496. What about a 502?

Re: Making the switch from 454 to 496 ho
 

What is the upside of a 502 compared to a 496? I have a good line a used 496. Do you have a turn key 502 for sale?

Thanks
Lt.

Re: Making the switch from 454 to 496 ho
 

I do not have a 502 for sale. Do some research on the 496 or start a thread on 502 vs. 496. If you plan on really running it hard or modifying some day I fell you would be better with a 502. I think there may have been a post on 502 vs. 496. Perhaps others will chime in.

Re: Making the switch from 454 to 496 ho
 

www.1800runsnew.com is the sourse for 502 longblocks. I had a pair and was happy with them.

Re: Making the switch from 454 to 496 ho
 

the 502 mag has forged internals, the 496 does not. if you plan on adding a blower, go with the 502.

As for props, you will probably stay with the 23. The 496/502 rev higher than the 310hp 7.4, so your rpms will go from 4600 to 5000 and thats where you will pick up the speed. If you go to a 25 mirage, you will have to have it labbed to get the rpm in the correct range.

Re: Making the switch from 454 to 496 ho
 

I'm shocked a 310hp Merc pushing a 27' boat would spin a 23" Mirage...

What rpm could you see with that 310?

Re: Making the switch from 454 to 496 ho
 

Me too. My 496 25OL ran best with a 23 mirage.

Re: Making the switch from 454 to 496 ho
 

The 496 is "closed-cooled," meaning coolant circulates throught the engine in a sealed loop, however seawater (raw water) is still required to cool the coolant via the heat exchanger - so you will still need a water intake.

And there's nothing wrong with the 496 in its stock form. I ran mine hard for 300 hours without a single issue. I know guys with 1000 hours on their 496s.

Re: Making the switch from 454 to 496 ho
 

I would think it would turn it, just around 4200 if i had to guess. my brother had an H2X with a 310hp 454 and a 23p and it would turn it 45-4600.

I would get the 496 is there werent any plans of a supercharger.