05 EX 496 ho's. every once in a while the warning
alarm will sound off and the engines seem to
loose power for a split second. All gauges normal
All fluids full. Usally will only do it after running
at around 3200 rpm for about 15 minutes.
Once it happens it usally wont do it agian for
the day........any ideas?

the alarm going off and loosing power is the mtr going into gaurdian mode the only way to see why is to scan the mtr and look at the time lines gaudian, the 496 has many resons for it to happen and there is always a reason may just be a bad sender or could be something more serious


the PCM 555 ( computer ) stores a picture every time it goes into guardian and all the paramiters each time a fault code is registered

Any dealer or someone with a DDT can pull the code from the computer and tell you what is sending it in the protection mode. My buddy had a 496ho and went throught the same problem. One time it was a false reading by the oil pressure sensor, oil pressure was to high, another time the water pressure sensor went out, had water pressure, the sensor was telling the computer he didnt. Got so frustrated finally built a N/A 540 and sold the 496.

no offense beak but trying to diagnose the PCM 555 with a DDT is like trying to fix a computer with a test light, yes it will show the codes but not much more

you want to find a shop that has either the Merc SPX or Rinda Diacom software both are laptop based and will tell everything that mtr does and did

The DDT was great for the older efi and mpi motors but the PCM555 is way past the DDT s limited capabilities

I wonder if thats why the repair shop had such a problem finding the problem with my buddys boat? They ended up changing the whole wiring harness in the boat and still had problems with the guardian mode, something would always send it their, and it was always a different problem, according to the shop.

Yea, I had my dealer come over and check it out. ( still
in warranty). Said they couldnt find anything. My guess
is they just checked for codes. Unfourtunatly,up here
most marine mechanics are woodchucks with no real
knowledge. As computers become more safisticated,the
techs have to upgrade their training..and knowledge.
I am a auto tech by trade and completely understand these
systems. Problem is, no software to check it out. Can
the program be purchased for a reasonable price?

yes the rinda/ diacom can be purshased for about 600.00 here is a link to it, it includes everything you need except for the laptop


it is a great program I like it better then the merc spx (I have both ) and its a lot cheaper too

www.rinda.com