Has anyone here taken out a 454 carb (330hp) and did a 496 ho repower? It looks like this is what I want to do, and im starting to research on what people ran into when doing it. My plan is finding a low hour 496 take-out and replacing my 454 because I want more hp and efi. The 454 is running great so once its pulled I will be selling it on here. What gear ratios did they change the drive to if they even did?

Thanks in advance for any info.

What kind of drive and ratio do you have now. Will probably have to re-prop no matter what

Im pretty sure i have a 1.65 bravo 2 with a 21p 3 blade alum.

I found a site that says all the mounting measurements and locations are the same as the 454. How did people wire for the efi? What kind of fuel pump did they use in place of the mechanical one?

The wiring is self contained on the engine itself. You can run them on the ground with a battery and a merc dummy plug. The round Merc plug from your old engine will plug right into the new. That plug is for on/off and gets info for the gauges and alarms. Hook up your power and grounds to the engine/starter and go.

As far as the fuel system goes you have a little work ahead. You will need to add a return line for the EFI system. And an electric fuel pump. Raylar is the guy you want to talk to, he should have everything you need

Thanks!

Im suprised there are no write ups on here about it....

i am replacing a 454efi with a 496HO right now..fairly easy for me,as the 2 are injected...bought a 496/whipple right here on oso...i agree your biggest problem will be with fuel supply/return...an aeromotive fuel pump should solve your problem
also if you buy a 496,make sure you get the exhaust system,as the two dont interchange

You don't need a return line or a new pump. Everything on the 496 is self contained and ready to go. They were designed to drop right in.

you're right....my mistake

Keep the carb....

I made that engine change. The exhaust was a little tricky since the thru-hull dimension was different but it was worth it. The 496 added 100 HP to my boat and it's a much sweeter engine because of the EFI. Carbs are yesterday's technology.

You should consider picking up a mercury SmartCraft guage to go with that engine. It's easy to install, inexpensive and very useful.