5.7 MPI questions...?
 

I have a 02 5.7 MPI and was just curious what the HP limitations are on the stock heads...? meaning if I wanted to re cam where would I stop making hp due to restriction in the stock heads...?

the ecm is set up with the correct calibration from the OEM being a stock application., Whatever gets changed from the engine side one will have to calibrate a new tune for matching all that. Timing, rpms limits, fuel mapping, fuel pressure, octane of the fuel and so on.


Also possible the increases of HP and TQ the injectors might get maxed out for duty cycle. This , depending on how much those increases are and requirements of the fuel injectors..

I don’t know the answer to your question on where the heads max out at, but if I remember right the vortec heads need a special set of springs to go over .480 lift.

On the tune, check with mark boos at precision marine. He may have a tune he can give you the combo to run with.

Vortec Heads will require machining with any lift over about .480 as stated. A few years back I built an engine for a C18 Donzi with vortec heads. I started with a 2008 Mercruiser 6.2 Longblock, bored .30 new forged pistons at 9.6 to 1 a GM Performance parts hot cam kit and the Vortec heads that were on the 6.2 Had the heads reconditioned and had the machine work done to accommodate the springs and hardware that came with the kit. The Valve guides needed to be cut down , Spring seats cut, pushrod holes drilled to 7/16 (not for larger rods but for clearance due to higher lift). Topped it all off with a edelbrock performer RPM marine intake and 750 carb and it ran great. 12mph over the stock 260hp 5.7 If you want info on the heads you can google gm vortec 906 or 062

Being a 2002, and if its a MEFI and not 555 then there would be several, could even do it your self with MEFIBURN and AFR meter

Could also go from 5.7 to 6.2

What boat is it in? Not all boats are going to respond the same to a 50-75HP Increase. Most likely all of your increase will be at higher RPM without increasing the displacement. If you are in a heavy single engine, you may be disappointed.

. It in a 330 Sun Sport formula

. How do I know what I have..? Its a 2002 Formula SunSport 330 its a 5.7 mpi Horizon. Serial number begins with a 3

Not seeing a Horizon starting with a 3, the serial number would be a number, letter and then 6 more numbers exp: 0M123456

Now if its 0M3 something then its probably 555

Yes 0M3

Then yes its a 555, and the range of remap is smaller but still do-able

No need to hide the full serial number unless its stolen, no one can do anything with it except provide info to help you

Was thinking today, if these are still made they should save you the machining on the heads.

https://www.hotrod.com/articles/vort...pring-upgrade/

Prob need to find out what exactly you have for one so that all the replies are not wasted space. Also engine(s) serial number is needed.

Big question is ---- I take it you have Horizon engines then do you have inboards direct drive or V drives ??

If this is the case then you will be hugely wasting your time. Inboard engines do not offer trim and the prop selection will be the next road block. Just saying

And for the record there is only 4 people in the USA tuning 555 ecm s / pcms. One of them is right here so that leaves 3 others. That's it.

And tuning thru the mail really is not the greatest either especially when a build is not a common performance build for a tuner to just throw a tune at it on his desk instead at the very least on a dyno or the best way would be in the boat - on the waters you boat mostly at and the pump gas you mostly are going to use along with that octane rating. . Remote tuning can work also.

. The only reason i know the prefix is because I ordered vessel view and they asked if the fjrst digit sdigitd with a 3 lol I have no idea the rest without lookin at my booklet...

Ya know, for the money it almost seems like switchin to a FAST XFI might be esier. There basic unit is 850ish. All its doing is controlling fuel and spark..

That’s a big boat for small blocks my customer has a 2001 Formula 280 SS with the same power. His boat runs great for a heavy wide boat with Bravo 3’s if I remember correctly it runs 57 or so light on fuel. He was going to upgrade to a 330 SS like yours and we looked at 2 for him. They were both big block boats. I am assuming your boat is small block due to Mercruiser not having a BB in 2002 from what I remember they dropped the 454 in 2001 and 496 didn’t show up till 2003 now due to build date some 496’s may have ended up in 2002 boats and some 454’s may have also. I kinda feel that you may not be happy with the speed gained vs money spent in a big boat like that. May want to think about selling small blocks and repower it with a pair of nice used 496 HO’s or something

mercruiser had the 496 8.1 HO MAG and MAG out Nov 2000 for model year 2001. I had them in new boat sales and in 2000 I had training classes on them as well. If I even recall in 2000, I was in a Flagship marine 8.1 class, The owner and his employee taught the class. Their engines had Mefi 4 ecm s compared to Merc with 555 pcms

Well I guess I stand corrected. Thanks for the correction BUP I always thought there was a gap in production and that was why Mercruiser started building the 6.2’s

Could replace the 5.7 with 7.4, 8.1 or 8.2 without much difficulity except cash flow.

I believe only donzi ran the small block horizon (vdrive) motors with bravos. Those intakes are better ,but the injectors suck. May be a option to swap to that intake and use a stand alone , or your current efi ,if you can get the injectors to work. A carb will attach to that intake also