Can anyone direct me to a chart that shows what gen Mercurser motor were made in what year?
I want to know about gen 1 and gen 2 454 and 502 EFI

They had v belts vs serpentine, the plugs on ecu plugged in ends

MEFI 1 was 1993-1995 ish (they may have begun earlier but I can't confirm that), MEFI 2 transitioned in 1996 for a brief period, then it was pretty much MEFI 3 and above after that.

If you have the engine serial number that is the best way to find out what it was originally designed with.

Or is the OP asking about Mark IV, V and Gen VI ?

I'm not sure, but a possibility.

Or vst gen 1 and cool fuel version gen 2?

[QUOTE=SB;4417562]Or is the OP asking about Mark IV, V and Gen VI ?
Pretty sure thats what he meant, at one point i may have referred to mefi1 and mefi 2 motors as gen 1 and 2 which i meant mefi 1 and 2. V belt motors w vst tank and end plug ecus

1993-1996 MEFI1/VST fuel system/V-belts. 1997-1997.5 MEFI1/cool fuel/v-belts.....1997.5-1998 MEFI1/Serpentine/Cool Fuel.....Either 99 or 2000 went to MEFI3/Serpentine/Cool fuel

Grim? I see the different configurations you listed but I do not see which one is a Gen 1 Gen 2 Etc....

Theres not really a gen 1 or 2, you may have seen me refer to them that way in other thread but i meant mef1/2 on gen v blocks w vst and usually v belt pulleys

MEFI 1993 thru 95 the largest ECM - VST systems

next was

MEFI 1 medium size ECM 1996 thru 1998 and MEFI 1 software in a MEFI 2 case - Some VST systems and 1996 was the transition year for Gen cool fuel for all year models 1997.

Next

MEFI 2 - medium sized ECM - GM 1996 software in a MEFI 2 case with GM part number 16210729 the 729 is the true MEFI 2, if any other part number without the 729 its a MEFI 1 software in a MEFI 2 case. Again the only true MEFI 2 carries GM part number 16210729. This was used on 350 MAG and the L29 454 only, (the true MEFI 2).

Next

MEFI 3 very very late 1998 / for 1999, it was a smaller ECM than all past MEFI's. All MEFI 3 Gen II cool fuel

Hope this MEFI info helps whomever