PA.WOODCHUCK

MEFI 1 - 2 -3 what's the differences in each version and advantages? Just want to learn...

Trash

MEFI 1 was the earliest and simplest. Easiest to learn if you want to tune yourself. Least amount of fidelity but will work fine in non boosted applications. If you have a MEFI 1 currently and want to build a NA motor it would be fine.

MEFI 2 slightly different than MEFI 1, but for all intensive purposes the same.

MEFI 3 had significant changes in ability to tune and added fidelity, but takes a long time to actually upload the file.

MEFI 4a/4b probably the most robust and popular, but more complex to tune but can be used in boost applications etc.

IF it was me and I had an existing MEFI system and associated sensors and controls I'd use it. If starting from scratch I'd opt for one of the Holley marine systems or MOTEC.

BUP

For Mercruiser a MEFI 2 --- A true Mefi 2 with MEFI 2 software was only in the 350 HO mag and the L29 7.4 L thats all. This info was taught in Merc class for many years.

MEFI 2 case with MEFI 1 software was in everything else from 1996 thru 1998

MEFI 3 was in 1999 thru the end of 2002 for the small blocks and 4.3 -- MEFI 3 for the big blocks stopped in very very early 2001 cause the 496 was out with PCM 555 totally different than any MEFI

Backing up info ---- MEFI 1 a true MEFI 1 with MEFI 1 software was 1993 thru 1995 and that had Guardian mode only/ Until one got to MEFI 4 and up 5 thru 7 as well.

KEM is using MEFI 7 NO OEM marine manus for new engines use MEFI anything for the past maybe 4 years or a tad more.

MEFI 1 thru 3 are NLA. The conversion is MEFI 4.and harness adaption if one wants brand new .

PA.WOODCHUCK

Thanks for the replies and education. That said I have a 1997 502MAG and wondering what upgrades I can do over winter for added HP without going forced induction. Open to suggestions and what would be expected gains? Procharger offers a kit to make 600+ HP Bolton but states if engine bumps limiter it goes lean then BOOM because limiter shuts fuel off at 5050RPM. I'm thinking about 500-525hp is my goal.

thanks