bn

I just bought some used 496 HO PCM's to convert my Mags to HO's. Is there any way to test them or look at what program is on them without connecting them to the motor? Can a Merc tech with a scanner verify that they are HO PCM's and verify that they work properly?

Will Merc put the most current program on them (for a fee of course) if I send them back to Merc?

GOODT

merc very funny about reprogramming 555 computers, try arizona speed

Raylar

If they really are 496HO ECM's they will say HO right on the white bar code labels on the face of the ECM. If they are 375HP Mag ECM's they will save "base" on the label. The Merc scan tool can be hooked up to the ECM's only on a Merc 496 harness that has the data plug in place. If this is done with power on the scan tool will indicate if they are HO ECM's. The history can also be read from the scan tool which will also tell you if there was a trouble code for a bad ECM. Remember, unless you change the camshafts to the 425HP type the programs in an HO ECM will not work correctly and the motors will not run correctly or make 425HP.

Ray @ Raylar

GOODT

true

bn

Something seems wrong with one of the PCM's. They both have 2 of those stickers that Ray mentioned on top of each other. The one has an HO sticker on top and an HO sticker underneath when I peel back the top one.

On the other one, the sticker on top says 496 MAG HO, part number 863619. When I peel back the top sticker, the sticker underneath says “496 MAG”, part number 863618. This is what concerns me.

Ray, I am buying the cams from you and most likely the polished manifolds and risers.

Brian

GOODT

merc had a service bulliton several years ago for what they called trailering effect, which was basicly for the black on the back ok of the boat ..... more then likly its because merc updated the pcm to the new specs