whistler

Any thoughts on why both IAC's would trip the alarms on the same day? It led to needing to replace both of the ECM's.
This is on a 2007 382 with the 600's. The guys at Merc. haven't suggested any reason yet.
I've been thinking power surge while plugged in at the dock.

BUP

iTrader: (9)

R U sure that power surges did not knock out your computer(s) first ? Just asking as I am very interested in this topic. Plenty of IAC failures have knocked out ECM's especially on the 496. Anyways so will bad coils FYI. I would watch out for that as well.

Any of the IAC cavity's and the IAC internally itself have deposits of belt dust, carpet fibers or grit ? How clean or not do you keep your flame arrestor ? is this a saltwater app ?

Did your IAC harnesses / plug in / wires have any melting or burned spots on them ?

Is all your battery connections and grounds very clean and very tight. Mercruiser & Mercury along with the rest of the OEM marine engine manu's do not want wingnuts for battery connections anymore. Just passing that along.

whistler

I believe the surge happened during a storm at my house. Everything on the boat was fine the next time we went out. An hour and a half into our trip the port iac alarm went off. Everything else seems to be fine. Alarm stops. We spend the night. Come home the next day. The port sounds again. Got home and started flushing engines. Now the port and starboard alarms are going off. Port iac shows no visible signs of damage. Starboard iac is fried. By the way salt water on that trip but usually more fresh then brackish. Service tech comes over, plugs in and says ecm failure.
Thank you for your feedback. I'm going to check into those other items you mentioned.
Unfortunately our season has come to an end.

BUP

iTrader: (9)

I have a story. A lot of marine techs around the USA talk to each other or well it seems for some reason I do with them and they do with me. Anyways. A tech from Sarasota Florida called me up (this was a couple of year ago) - he was working on a twin app Mercruiser / Racing 600 SCi's. One side motor ran great, started great and scaned with no fault codes, the other side motor - had a no start and would not even scan nor connect to Diacom. I told him sounds like a BAD computer on that side 4 sure. He agreed. I then said to him do this later on, swamp out the ECM from the other good motor but make sure you don't have any bad ignition coils or a burnt up IAC or connections before doing so.

So while we are still on the phone talking he is swapping out ECM's, I had no idea. The next thing I hear in the back ground is he is cranking over the bad no start engine. I hear a bunch swearing and so on, and after that he asks me now what, I told him, you better plug in diacom to the engine now to see if anything will pull up and I hope you are able to connect. He then says guess what, I can not connect now or get anything to read from diacom.

The short list of the story was the good ECM got fried right on the spot just by him swapping it over and cranking the motor over a few times without the motor ever starting. It turned out, 3 bad ignitions coils on the no start engine caused both ECM failures. They are not cheap to buy either.

whistler

Thanks for sharing that one. Do the bad coils show up on codes or act up in any way as a warning?

sutphen 30

should show as a bad coil or a misfire in that cylinder.
also,if you have twins,switch supposed bad parts over to good engine to see if the problem follows.

Got Freedom?

It is a very common issue that the IACs in the 600sci and 700sci motors short out and then take out the ECM. NEVER swap IACs or ECMs between engines without checking for a short first. You can send your ECM to Whipple to be repaired for a lot less than the cost of a new one. I have had IACs fail within a few minutes of each other so I don't think a power surge is your problem. To my knowledge there is no known fix available from Mercury. I recommend installing inline fuses to protect the ECM and carrying a couple spare IACs onboard.

GF?

BUP

iTrader: (9)

That was the point to my story. You have to find the cause of what caused the failure to begin with and fix that first before you do any parts swapping and or mixing or new parts replacement. Also no offense to anyone but most do it yourselfers and marine techs who are not that indepth trained can do more harm than good sometimes when working on marine apps.

Again you have FIND & FIX the cause or whatever related areas that caused the failure to begin with then move on to that exact part failure. Sometimes it is just that part that failed on its own but many times, its something else that caused it. .

BUP

iTrader: (9)

There is more to it when you scan the motor to find bad ignition coils. For one if there is a problem with any of the coils it will not show on your scan listed in the fault code or history "bad coil" or even the word coil or even the word bad. Anyways. There is a couple things to know. the 600's & 700's and whatever else used that exact coil can have there problems. Also the earlier 496 coils were junk. The 496 changed coils to a second gen but I forgot what serial # break / year approximately. Want to say 2004 or 2005.

The fault code that shows up and the explanation as I have this imbedded in my head.

The fault listed when scanning with Merc CDS will show EST 1 Shorted Circuit or EST 1 Open Circuit - depending on which coil to which cylinder #s. The numbers can list 1 thru 8 depending on which coil or connection or wiring can be the problem.

The Merc DDT fault status and diacom will show EST 1 shorted or EST 1 open and again depending on which coil in relation to which cylinder the numbers go 1 thru 8.

There is a kicker as some techs can get confused thinking they have a bad coil(s) or problem area..

the reason is.

less just say you have a EST 1 short fault code ( meaning coil #1 problem area) as when ever the fault lists short or shorted it will mean Ignition fault. And the signal from the ECM / PCM to the ignition driver module is shorted. This is only detectable when the engine is running as per the ECM / PCM reads RPM's. It will never show without RPM's logged in the computer during that time.

The possible cause of this fault could be a connection problem (ignition side) thru out anywhere in the system per coil, it could mean a faulty or bad coil problem itself or it could mean a wiring problem that is effecting the ignition side especially that exact circuit the listing # is for. it could mean a spark plug wire problem as well.

Hers is the kicker the EST 1 short or shorted will show up or possible show up in ECM / PCM 555 and PCM 09 controllers if you are bumping off the rev limiter. If so this should also show an OVERSPEED FAULT as well. During overspeed the ignition trigger signal is being turned off. It is not wise to keep bumping off the rev limiter (overspeed ) for many reasons. the big one is you are dropping spark, not fuel in most cases. if you have an overspeed fault and an EST fault it might not be a bad coil - or plug wire or connection - or wiring problem at all. The computer is doing its job turning the ignition signal off during OVERSPEED. Actually protection mode to a certain point.

Next if the fault code shows EST 1 OPEN it means ignition fault. the signal from the ECM / PCM to the ignition driver module is open. This is DETECTABLE at 0 RPM only. The problem could be bad coil, wiring problem or connection problem all leading to the side of the ignition system per fault listing whether 1 thru 8 (coil & cylinder #)

I hope this helps and how to detect a possible bad coil and when it is not a bad ignition - coil area even showing a EST fault. SORRY for the novel but very hard to explain in a short story plus this is how I learned it many years ago and it was a huge story more than this.

paul buckner

BUP can the later/ better coils fit on the older 496 ho I have the 2001 mod , also Rock auto parts are listing coils in there marine section For the 496 would thes be the better ones ?