496 MAG-HO running issue
 

Engine number 0M084807 2002( 175hrs), here's what happened today and don't have more info until I scan the engine Sunday. Been running about 30 minutes and all was OK until I came off plane and noticed engine maybe misfiring. I shut engine off and all looked good and restarted a few minutes later and ran normally even running to max RPM. Here's what I have so far.. when first uncovering boat found new cover let water into boat and when opening engine hatch there was condensation all over engine. Also waiting for feedback from former owner to find out where he got the plug wires along with what brand? Besides doing the PCM scan does it also detect misfire and set faults as I didn't get any fault beeps while running.

Also had an open recall done which was for if engine can't be turned off a addon harness needed to be installed. That bulletin no. is 2001-14 which I have another question since the harness plugs into the 10pin can connector. Mercury stated my engine doesn't have "smartcraft" even though there's a tag on transom housing stating otherwise.

thanks
more info to add another day.

Back from doing a scan which I attached. BTW, log is from day one, and going to clear everything to start new history log. Looking at plug wires the only markings is "Packard" and no mercury logo.

BUP, chime in on this and will call Monday and may e-mail today. At this point I think the plug wires are the cause with my 40+ years auto experience.

thanks

the open recall was a bad diode for the engine not turning off at the key switch just a side note for whomever. It was good you posted your serial number. You guys are learning haha just messing cause I bit ch about that all the time.

Spark plug wires one has to watch out for emi and rfi because some brands do not provide enough surpression and will cause running issues actually lunch eater issues. Just another side note. . There was really good thread / post up here where a boat owner on his 496 installed Taylor spark wires and had hell - short jist the fix was swapped wires back to Merc and all was perfectly good. I can not find that post so if someone knows where it is -- post the link because that is a great post, exactly what I am talking about for EMI / RFI .

Anyways im sure some will say you have a bad this and that inwhich there is some bad here and there is NOT bad either according to your scan but will be suspected. It would be best per phone call so I do not have type out a story book,

Actually this is a good thread for people to look at the scan and post what the issues at hand are.to really learn about. Just because you have the scan tool whats NEXT to fix this correctly ? Lets see who can find whats good and whats bad in the scan.

agree 100% with you
a couple of guys on here are real quick to advise someone to go out and buy a scanner,I always thought ,what good is a scanner if you do not know what the data/information means?
just because you find a code stored for a TPS it does not mean you have a bad TPS,you must have the training and the ability to diagnose and repair correctly,

I would never go out and buy a stethoscope,just because I can use it to hear my heart ,It does not mean I know what the heart beat means,LOL

Kind of like the debate in your world with P0430 codes. Is it the cat or is it the O 2 s or what is it for catalyst system efficiency below threshold. Im not just going to start pulling the cats and all O2 s and hope I get lucky with throwing new parts at it just because I have a fault code.

Adding about how the boat industry has become --- The marine cat engines are NOT for attempted fixes by people whom are not trained on them period. Thats a whole different animal right there as 99 % will cause more damage. Believe me I know because thats the only way the boat owner will bring their boats in for service / repairs when its totally jacked up and they have ran out of ideas and finally aware things worse to even a no start condition or have to get towed in from the lake many times.

I only posted this because thats how it has become for me and others in the industry. I do not get the easy jobs - I get a completely jacked up unknown puzzles and it has alot of missing puzzle pieces to fix. Can you imagine the auto world being like this ? not even close. When joe who has to be at work everyday, He is not going to jack his truck up and pull his broken tranny out to fix on his 2012 Ford 150 himself but - he will have it towed and fixed at the tranny place or dealership and pay deeply out of his pocket without a blink of an eye but if Joe tranny goes out in his boat, he will pull his drive and go about however for all the attempted fixes as a boat dealership is not even on his radar to get it fixed. . Am I right ?

If someone wants to DIY, why wouldn't you suggest a scanner ? And why wouldn't one come to the forums ? That's what they are here for.

I'm one that is an advocate to own/share/rent/borrow a scanner, and I won't deny it. Does it fix everything? NOPE. Does it fix ANYTHING? Actually nope, it doesn't do that either.

BUT, it sure beats jumping on the internet and stating "my Mercury/Mercruiser is beeping, please help".

If you have a sensor that is setting off an alarm, it sure helps having a scanner to see what that sensor is, and IF you have a twin engine boat, sometimes it makes quick work of swapping sensors to diagnose the issue...
...vs. trying to get an appointment with your marina, get the boat there, wait for them to get to it, costing you a ton of time and money just to GET there...
...before they even have a chance to diagnose the boat. My time IS worth money, and having a proper scanner proved it's worth to me, many, many times over. Especially if the aforementioned was in the dead of summer and a big boating weekend was coming up. Plus, I can't count how many times I loaned it out at a Poker Run to help a (new) friend.

I like when I tell a customer he has a P0430 or a P0420 Bank 1 or 2 and does not want us to diagnose it any further,takes it and replaces the cat/converter himself and comes back a month later complaining that we misdiagnosed and has another melted cat/converter all because he did not want to pay for diagnoses ,little did he know the 1st cat failed because of a rich injector/bad coil/vacuum leak,etc, easy to diagnose if you know what a good reading versus a bad the reading is.

again a scanner might be ok for pulling codes and having a 50/50 shot at fixing it by throwing a part in,but if you really want to use that scanner to its potential ,you must be trained.

I hear you I know a tad about the auto side but am somewhat trained on it because of how the marine side went with VVT and GDI - I went out and hit whomever I could for classes and sems about this 3 years before it ever hit the marine side. I was 3 years ahead of any marine tech in the industry. Even adapted my fuel injector side to GDI as well so I have both covered.

Anyways - Like I said one has to watch out for the marine cat engines because they have so many newly related systems that even marine techs screw up. The cat themselves can be very problematic -- ie --- run the boat out of gas and you most likely blew a hole right thru the cat . For one side is a 3 K min repair again just for one side.

Anyways back to the post at hand here --- the OP posted a scan report and that is a good way for people even without scan tools to throw opinions and or what they think is wrong here. No comments have been made but the choice is up to whomever..

So what does anyone think about the faults showing from the scan ? Are they the issue at hand or ? what is taking place from the scan ?

Actually it is best to scan the engine in the water under load and thru out different rpms as well - one can logged or write down those parameters cold idle - warmed idle - 1K - 2 K 3 K 4 K and WOT if one can get WOT out of the engine(s) .

What is showing so far is decent for a start of info to help lead someone in a direction for a possible fix especially without hands / eyes / ears and tools on it in person.

Opinions or whatever does anyone think ?