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2005 496 Mag HO intermittent shut off

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2005 496 Mag HO intermittent shut off

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Old 02-02-2019, 01:38 PM
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Default 2005 496 Mag HO intermittent shut off

Have any of you ever experienced this... boat is 2007 Baja 30 with twin 496 Mag HO's cruising along at about 60 (4000 rpms give or take) and port motor started to drop out for just a brief second. What happens is rpms drop to 0 and solid beep but just for a second then she's right back on. Of course this is quite noticable cause you feel the power loss. Just taking a long shot to see if anyone has had this happen.

Thanks in advance for any feedback.

Brian
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Old 02-02-2019, 01:55 PM
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Yes and I fix them all the time its your PCM internally is bad with a certain chip in it and 3 other components. I Just fixed 2 of the same exact issues last week. This is a very common issue and 90 percent is a Voltage issue on your end and or the engine side that caused this failure inside the PCM.

Also you will need to completely go over all the IAC system area parts and that maintenance as well. I have all that info and CORRECT PARTS as well. The lack of doing so will knock out those components internally of the PCM 555. This is just a jist of info about all this.
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Old 02-03-2019, 10:10 AM
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Thanks BUP
I did look over the whole IAC circuit I replaced the two little mufflers in the intake housing. Also inspected the wiring but is there any other maintenance to do other than R&R on the IAC valve itself? Also how can I get the repair done on the computers? Do I have to send them out to somebody for a reflash or something like that?

your advice very helpful and appreciated

Thanks again

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Old 02-03-2019, 10:42 AM
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Personally I would make sure you have a good clean ground,also make sure both engines have a good clean ground cable connecting them together,I would also check and make sure your batteries are good with clean connections,if you are still thinking its the ECU ,I would disconnected the batteries ,let it be for about 5-10 minutes so the capacitors inside the ECUs drain (this is to prevent any voltage spikes) ,switch ECUs from engine to engine and take the boat for a rice,if the issue follows to the other engine then replace the ECU,if the issue stays on the same engine then continue diagnosing,
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Old 02-03-2019, 11:10 AM
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Its the PCM I promise and I know what I am talking about here. I do this REPAIR ONCE EVERY WEEK many boaters send me the videos of their boats experiencing the exact issue as you describe.

99.99 percent of shops and people do not know what this issue is and struggle for a long time fixing this exact issue.. Some take years to finally get it fixed correctly.

If you want to send your PCM in I already know what is wrong with it. NO BS then next step is to talk in details how not to have this issue again and I have all that info and the correct parts

And for the record I just fixed 2 last week with exact same issue per your posting.
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Old 02-03-2019, 11:23 AM
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Have to add this for boat owners who do their own TESTING. I understand you are trying to solve issues but here is an example how you can create double the bad issues and double the expense. DO NOT SWITCH ECMs PERIOD

You have a huge chance of knocking out the known GOOD PCM 555 by putting it on the bad running engine. I am already saving you money and I do this for a living,

Marine ECMs suffer way more than auto ecms for a jist of info and most of the times its Voltage issues or self inflicted by the boat owners that knock out the ECM / PCM,

the way to test this without harm to a KNOWN good ecm / pcm is to take the known BAD running engine - take that PCM off and put it on the good known running engine. then see what happens. But in twin engine apps that is hard to do because you do not what to risk the known good PCM / ECM putting it on a known bad running engine. Yes that can take place - hurting the known good PCM / ECM and putting it on a known BAD RUNNING ENGINE.

Added info on top of --- bad ignition coil(s) can knock out that driver inside the PCM. I Fix those as well. A bad IAC can knock out that circuit inside the ECM / PCM among many other things that can knock out a ecm/pcm

Just because you switched out the IAC means nothing - what is the scanning parameters of the new IAC when running at idle and thru out all rpms ?? there is many more parts to the IAC system that just replacing the IAC and muffler. Is your flame arrestor SPOTLESS clean for one example ? does engine running create best dust ??? another example of issues that hurt the IAC system.

anyways your pcm is the issue and it was cause from something on the boat side or self inflicted by a person

If you decide to send your PCM in to me let me know a timeframe I am overloaded. THX
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Last edited by BUP; 02-03-2019 at 11:55 AM.
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Old 02-03-2019, 11:50 AM
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I want to tell this story. And it was a marine tech located in AZ. He had a boat with twin Volvo Penta 496 s. it was 2008 model. e controls for ECM s. His shop was working on it, last month.

One engine would not start nor would the fuel pumps turn on at all.. He did everything and change out with a whole new carter fuel module at 1500 bucks - the relys - and fuses and so on. Still nothing. so he switched ECMs - he had a 100 % good known running port motor like I said it was twin engine app.

He swapped over the ecms and just by him cranking over the bad engine with the known good ecm -- he knocked it out (the known good ecm ) in 20 seconds.

he swapped back over the ecms and then realized he NOW had 2 engines that did not run nor turn the fuel pumps on. He found me online - called and told me the story --- sent me the ecms for testing and repair. Both fuel pump drivers and circuits were completely knocked out inside the ecm. anyways the issue was on his engine side - it was in the wiring harness.

Short story and a 100 percent true story. Just saying and this is not the only story I have about knocking out the other engine ECM. I have many more

Last edited by BUP; 02-03-2019 at 12:27 PM.
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Old 02-03-2019, 12:14 PM
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here is a good example of what I am talking about Yes it is Merc outboards but yes its PCM 555 as well --- the exact same is true for many apps . ESPECIALLY the Mercury Racing 600 Sci and 700Sci and the all the 496 s. Read it cause it happens more than you think. And can ruin a NEW and or known good ECM / PCM just by cranking the engine over BAD IGNITION COILS, and of course there is other things that can knock out the ECM. I am just trying to help boaters out and all this time and advice is on my dime.

http://www.marinepartsexpress.com/Me...02007-25R2.pdf

Last edited by BUP; 02-03-2019 at 12:18 PM.
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Old 02-03-2019, 12:16 PM
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Okay so tried swapping to ecu's and the port motor still did the same thing. I have to tell you a little bit of backstory here though. Recently we put the boat in the shop because I needed the water intake hoses changed and just do not have the time space or all the tools to do it myself. Once I got the boat back I noticed that I wasn't able to get full WOT rpm out of my port motor. Then when we were running hard I would get that intermittent shut off and beep. I just realized today that my drives were over-trimmed due to the fact that it was probably improperly reassembled with the limit switches and all. Could over trim be causing a problem like that? I tried a hard run with my drives in more than I usually would have them and the boat ran strong without any Skip's. When I came off plane today the port motor was giving me the dreaded 2 beeps every 2 minutes making me think that the IAC valve on that motor needs replacing. Another thing that I did notice if this helps at all is that when I turn the key to the on position on the port motor the fuel pump continues to cycle it does not shut off after the initial few seconds it supposed to run to Prime the system. When I switch the ecms the starboard motor was doing that so obviously there is some kind of an issue in the computers. My question is could that over trim situation be causing the computer to shut the motor down?
I may want to send you the computers just to go over them and make sure everything is good. Let me know where to send them and what kind of a cost I am looking at.

Again any of your help very much appreciated
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Old 02-03-2019, 12:34 PM
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See Sometimes --- I guess right - see sometimes I am lucky and see sometimes, I am just that good. I ll let you pic one --- haha had to throw all that out there because you have alot going on with engine running issues.. Anyways your PCM is bad like I said and POSSIBLE BOTH NEED TO BE LOOKED AT.

it is best we talk over all this so that it can be fixed correctly and NOT HAPPEN AGAIN. BUT NOW I think maybe you have both PCMs with issues ??? . Yes I would love to take your money over and over again with many PCM failures but thats NOT want I am about. I want to see you have less issues and stay into boating, and do not want to see one go broke because they have to pour money over and over again for their boat..

With that said HERE IS MY ADVICE --- I WOULD STOP ALL TESTING NOW and unhook your batteries or make sure no power is left on - do not charge your batteries either at this point and timeframe if they are staying the boat ..

You are in NY -- how are you able to run the boat its freezing up there ? I do make trips to NY for events and have handful of customers up there. Born and raised in NEW YORK as well

U have more than one issue here -- Boat side and PCM side. One PCM has internal damage - I know for a fact without any doubt about that one. The other pcm is a question mark if something is bad internally. Testing it completely in my hands is one way to figure that one out.

If your fuel pump does not shut off that can be an issue internally with the fuel pump circuit inside the PCM. That can be tested in my hands

Last edited by BUP; 02-03-2019 at 12:59 PM.
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