The only way i knew was the error it was throwing on my Mercury System View of "Engine Fault - IAC Output".

I replaced the Idle Air Valve and kept getting the error.

I ended up sending my ECM/PCM to Whipple Superchargers for repair. They got me fixed!

https://whipplesuperchargers.com/ind...&product_id=73

SH,
Thanks for the info. Look like I might have a bad PCM.....

And this will happen again and again when Iac is defect!
It is importend to make in the wire to IAC an 1A fuse! That stopps the problem with defect Pcm after IAC trouble then!
Michael


https://www.offshoreonly.com/forums/...e-install.html

Anybody know what the chip is that needs replaced?

here is what it looks like

the fault is IAC output its either a circuit failure or the IAC itself. Test all wiring for the circuit and the IAC - Just throwing a new IAC can mean nothing for the fix.

AND here is the big AND - you guys all know there is SB for the open campaign of IMPROPER OVERCURRENT PROTECTION for the alternator sense circuit and starter solenoid inwhich causes this among other issues for a short jist of info.

It was large group of engine serial numbers this falls under. Many 600 SCi did not get back to the dealers to have this overcurrent SB performed. The big reason was the SB came out exactly mid 2008 when many dealers went under and alot of boats went out as repo and cheap sales bank offerings.

One needs to find out if their engine has had this SB performed. If not you need to. Also splicing into any ECM wiring harness and adding resistance changes the values inputs and outputs per sensor readings. Merc STRONGLY recommends not for any homemade wiring add ons or inline fuses per how they redesign for problems and issues..

I have brought this SB up before and needs to be looked into by whomever. SO far 4 OSO members engine serials numbers that I have checked into for the past 2 years - all 4 never had this SB overcurrent protection performed. One owner had a bad PCM and the other was having IAC issues per their words. These were boats NOT seen by me in person but owners whom wanted the service manuals and or help fixing their 600 apps.

This exact service bulletin also covers the hp 525 and the 700 sci plus 2 more Merc racing apps. Keep in mind the 600 and 700 sci are wired differently inwhich ends up being increased failure rate. Just putting it out there for the taking. Also I would ask whipplesuperchargers if they ever looked into this overcurrent SB ? Really do not know if they get any of this OEM after the fact info from Mercruiser and Merc racing. Not saying this in a bad way. But really needs to looked into.

chip has no markings on it,covered over,,I had a bad ecu that I took a good chip off and replaced the burnt one.very noticeable once the ecu is opened up.