Im building a 502 to replace my current 454 mercruiser. Bored .020 over, dart heads, should be around 600 hp once complete. My question is the mpi mercruiser intake does fit the 502, but is it going to perform up to par on the bigger motor? Or should i buy a carb instead. Also will the computer work with the new motor?

Just a guess, the intake was designed to work on the stock 454 and the ecm was programmed to work on the stock 454, what is the stock HP of the 454 vs what you expect to get out of the new motor. If the intake doesn't hold it back you will probably run lean.

I would say unless your 454 was a 454MPI horizon (385hp) with high rise intake I wouldn't use it on a 502

600hp, if the cam, heads, compression, and exhaust will support it...means throw the 454mpi and 502MPI intake in the trash. Even the 500EFI intake has a hard time getting their.

GEtting something like this with supporting hardware and computer will get her done:

Edit in: Holley made the below intake available with brass passages for marine..not sure if they still do.

Is your 454 a 454 mag or MPI. Totally different intakes. One is for Peanut Port"MPI" and the other is for Rec Port "Mag". I think all 502's are rec port so thats your first hurdle is figuring out what you have.
This is an MPI https://www.youtube.com/watch?v=DjKNG7LhOao

This is a Mag. http://www.mycobalt.net/2009/07/23/2...-223-for-sale/

Mag has the intake with the air cleaner making a turn to starbord.

Chris

If your engine is a MAG, the 454 and 502 MAGS use the same intake. And your computer will need to be programmed for the additional hp anyway. But, as SB stated those intakes won't flow enough to support 600hp.

You'd probably need new injectors as well and at the end of the day wish that you just fresh with a new Holley EFI system or the like. You could luck out and have it be perfect, but the stock equipment is just so unfriendly to any sort of adjustment. I looked into using my 454 mag system on my 502 and just threw a quickfuel carb on it and have been happy with that. I think that you'd have to use the original cam as well.

if the 454 was a mag motor that the mpi setup came off every part is the same inc injectors .the only diff is the ecm has to be remapped to a stock 502 setup .ask me how I know ive done many the cost for remap is 100.00 .never had 1 issue

You might need larger injectors.. They are not that expensive if you get them from rock auto. Yow will probably need and adjustable fuel regulator. As far as cam i would "think" a 500 efi cam would be drop in. Give bob a call at Marine Kenetics, think thats the name, and ask him. If you have a Mag Intake then I think this is totally dooable. Get the PCM flashed by someone like maybe whipple and your good to go. Not 600 hp but maybe close to 500

Chris

Another option and probably a better one is sell your entire MPI setup including Intake, cool fuel , PCM Dist and everything and Call Haxberry and order Holley. He can tune over the net to some degree. Prob get about 900-1100 for your current mpi setup.

Chris