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.

Re: Making the switch from 454 to 496 ho
 

Bajarunner you are correct about 4200-4300 with the 23 pitch 53 mph on gps.

I bought the boat this spring and I am ready for more power. As of right now I don't have any plans on increasing beyond the stock 496 ho. I have been looking for a 496 or 502 and found a nice used 496.

Are the accessories on my 310hp 454 mpi switchable to a long block 502? I see a lot of long blocks but not a lot of Turn key motors.

Thanks
Lt.

Re: Making the switch from 454 to 496 ho
 

I'd stick with your plan for a 496 ho. It makes mor hp and has significantly more torque than a 502 mpi. The electronics are much more advanced, closed cooling, better exhaust manifolds and risers.
As for your water intake hose it should plug right on.
Although it is true that the pistons, rods and crank are cast they hold up fine in stock form. In fact Raylars 525 kit utilizes these three stock items.

Think about it. Why would Mercury replace the 502 with the 496 if it wasn't better?

Re: Making the switch from 454 to 496 ho
 

A buddy of mine did exactly this conversion on his 272 last year. He runs a 23" Mirage Accelerator (its effectively about 24" because of the extreme cup). It is THE prop for a 272 because of the relatively low set drive. Expect 67 - 68 mph @ 4900 - 5000 and great hole shot and good grip in the corners. Maybe its not quite so grippy as a 24" Bravo but overall it is the best.
You can fit Corsa diverters no problem, but you need to use the ones with a slight offset built into them because the risers on a 496 are slightly wider apart than the 454/502 ones. Even if you didn´t fit silent choice you will be confronted with the problem of the holes in your transom being a couple of inches closer together than you need. Go the Corsa route, but get the right ones.
The 496 is a really good robust motor with fit and forget qualities. It suits the 272/275 really well. Ran great in my 25OL as well.
Closed cooling and Gaurdian/Smartcraft make it very reliable.
As said if you would want to fit a blower, the 502 has alot going for it, too.

Re: Making the switch from 454 to 496 ho
 

Wild,
Did your buddy have any problems fitting the motor in? Did he have to remove the rear bench? I pulled the motor mid summer to replace a spun coupler and it seamed a little tight.
Thanks
Lt.

Re: Making the switch from 454 to 496 ho
 

:D :D :D Just bought 496 :D :D :D

Hopefully I will still be happy when I do the install :rolleyes:

Thanks for all the input
Lt.

Re: Making the switch from 454 to 496 ho
 

I did a similar swap but I took out the 496 and put in a built 502. Like was stated above the biggest problem I had was relocating the holes in the transom.

Re: Making the switch from 454 to 496 ho
 

I went from a 454 Mag to a 496HO. The 40 more HP allowed me to go from a 26 Bravo 1 to a 28P.

I had silent choice with the 454 Mag but I removed it. I have about 18" of rubber hose, so, lining up the exhaust was no problem. I'm running straight thru hull. I don't think the 496 is really that load.

Everything else plugged right in. There is a Merc bullitain about the "fiber washers" in the rear motor mounts, make sure you have them in the correct sequence or the motor will not line up.

I have 115 hrs on mine with just a few minor problems. Do yourself a favor and buy a scan tool or diagnostic software. It will pay for itself.

The 496 is slightly longer and higher. Look at this pic, the extra inch or two in length was ALMOST a major problem for me. My 454 had a few inches of clearanace there.

Re: Making the switch from 454 to 496 ho
 

I'd feel much better/secure with a 502, carbed. Kind of like the 454's... tried and true, reliable as the day is long. Like others mentioned, rotating assembly is forged, not cast. In the end, a stronger engine internally. Tons of parts readily available for them for upgrades later on. Plus, all the bolt on stuff from your 454 WILL bolt on to a 502. And the holes in your transome WILL line up with the 502 exhaust. It's a clean and simple swap from a 454 to a 502. I know, 'cause I done it ....ZZ502/502 :D

Don't get me wrong, I'm not knocking the 496, as I know squat about them. I'm sure they're a fine engine.

Re: Making the switch from 454 to 496 ho
 

Cost.

Re: Making the switch from 454 to 496 ho
 

And related to cost, for the most part the 496 is what GM is pushing out the door, for now.

Is GM producing the 502 anymore?

Re: Making the switch from 454 to 496 ho
 

502 crate engines are available through Summitt and Jeggs, so I assume that to be a yes.

Re: Making the switch from 454 to 496 ho
 

Lt, the 496 is tight in the 272 engineroom. Take out the top part (the trimmed part) of the rear bench. you will have to remove the headers and lower the motor in sideways and then rotate it 90° once it is down below the rear valance. Taking out the rear lower part of the rear bench makes things alot easier!

Re: Making the switch from 454 to 496 ho
 

Yea I figured it would be tight but I had heard of several people doing the same switch so I knew it was possible. I dont think I will start the process till mid October.. Still a few good weekends left. Hopefully!!!

Thanks
LT.

Re: Making the switch from 454 to 496 ho
 

Will the wye pipe from my 454 fit the new 496 or will I have to get a new wye pipe?

Thanks
Lt.