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iTrader: (9)

I AM GOING BACK TO POST # 72 OF MINE.

I put my thinking cap on today for your lunch eater. I really had a busy day today but went out with my wife to dinner and of course we talk boats as well and of course the problems I see. I do a lot of consulting marine work for about 9 mom and pop boat repair shops. So I always have something marine related to talk about - good or bad or funny or stupid about boats. My wife is so cool about it as most women could care less. Anyways a little history of me but no big deal and not patting myself on the back.

Post 72 about your coil - your problem stems from the port side of your problem child engine. I am 100 % sure about this without even looking at it. You have a knock sensor # 1 code that is on the port side of the motor as I mentioned earlier in a replied post. (Its on the Port side of engine). There is a reason for your knock sensor code but there is a possibility it is bad as well. Here is what I think and it hit me at dinner today.

Your knock sensor is throwing a fault because your # 5 coil and or the plug wire and or the tower of the coil is leaking voltage either on the valve cover or on the metal part of the mount of the coil. The knock sensor - senses this arching voltage as why its # is so high and sets the fault.

You need to change that ignition coil out completely with a brand new one all of it the mount - the plug wire and boot and the spark plug(s). If it is not # 5 coil and everything else I said then change # 7 as well if that does work change # 3 . IMO # 5 should fix this. If it were my boat I would change all of them out but do # 5 first to c what happens.

These coils on the older 496 were problem childs anyways. Also go back an read # 72 post because I will say it again bad coils can knock out the PCM - I'll say it again a bad coil(s) can sometimes yes and sometimes no knock out the PCM / ECM. Good luck. If you do not listen to me on this or do what I have posted to a T - I say good luck keep on working on it or send to a certified Merc shop. If this works out for the fix what I am telling you - you owe me Christmas present hugely. LOL.

Also you could have a bad knock sensor # 1 as well but do the # 5 ignition coil first to see how the engine runs then move forward with other port side (complete) coils and spark plugs. The if needed move on to the knock sensor. My bet is # 5 coil / wire / boot / spark plug might just do it.

The bad ignition coil leaking voltage is your voltage drop hence why the tach goes to 0 as the motor sounds like its turn off real quickly and turn right back on. You are voltage dropping at the PCM not the battery. FYI

4Lance

One thing where is the grounds for pcm? Is everything on back lower of engines for grounds?

BUP

iTrader: (9)

Ok were are making a novel out of this. Where are you located city and state wise ? I hopefully can refer you to a good a repair shop that hopefully can get you back on the water very soon.

You need the proper service manual and the proper diagnostic manual along with wiring diagrams for the correct info if you want to continue chasing wires. it would be very wise to get all of this before you do more harm than good to your engine Good luck and let us know what fixed it or let us know what the repair shop fix was. I can hopefully give you a referral repair shop but need your location.

4Lance

Im in danville Illinois. I think the only place close would be Indianapolis Indiana? Just wished it was something simple and really weird had no issues till a starter replacement.

Im going to order a new knock sensor. Whats the odds by replacing it that it would cure everything?

And im sorry ive been dealing with this all summer first chipped lower tooth in lower unit. Then same engine started getting hot after drive replacement. Then it was hitting rev limiter which it never did . Then starter decided not to work anymore now this almost dying deal and then decide to see what it would do yesterday at cruise and then a quick wot run and now its only bouncing around 4900 rpms not ever going over 5000 like it did previously and to make matters worse the other engine is running around 400rpms less than other. Just been spending money like crazy when it makes me sick laster summer everything ran great I do appreciate you help

4Lance

Just a update I put another knock sensor on port side and ran again still does surging where it almost dies but under freeze memory on rinda scanner it doesnt show knock sensor 1 fault anymore where before it would pop up soon as it dropped rpms and surges back up.

I also wanted to check out overheat issue on this engine so I took hose of right side of power steering cooler and other end off oil cooler there was some stuff built up but now bad. So I backflushed system again from heat exchager so I could watch pressure out of oil coiler and it was shooting out pretty good so next I hooked garden hose to flush kit the forces water directly in front of pump then started engine for 10 sec to just see water psi with hose off heat exchanger and it just seemed like water wojld be gushing out but it just had a steady stream pouring out of it at idle ? Then I clamped hose back to heat exchanger and now im getting a alarm and scanner said sea water pump 10 high block pressure wth? And when running starting to fet steam and water is hot where before it wasnt I just put new impellers in both engines and had both rear plates resurfaced by a machine shop other engine is fine. Im about to give up this summer its one thing after another and money is getting tighter from all my issues

Also got new spark plugs to install 2mro

BUP

iTrader: (9)

So you are not listening to what I posted, Is this motor still doing like it did in your youtube video. Surging then cuts out - tach goes to 0 and then picks back up ?

Again for the last time your problem is on the port side of this motor leaking voltage or voltage spikes. Ignitions coils 5 first then 7 and so on. Next all wiring around the PCM and any wiring close to the pcm bracket and or going under it. This is what IMO is causing the PCM to drop voltage if in fact you still have the same problems as before.

Also it might be best to get a referral of a good Mercruiser shop in or around the Chicago area. In your area I do not know who or where to send you.. Maybe someone up here might post a good shop.

4Lance

Like you said first try replacing knock sensor I did and yes it is still doing the rpm drop like its shutting off. But like before it is not throwing a fault for knock sensor like it did everytime before.

4Lance

Hey tried to pm u but says mailbox full could u email me was going to see if you could give me a call

[email protected]

4Lance

http://youtu.be/od5uF7pDtko http://youtu.be/od5uF7pDtk

k finally got this loaded it was on gfs Iphone had to convert it and upload just so you can see what fuel does. I wish I was holding it in hand for the video

BUP

iTrader: (9)

U R Killing me. Electric fuel pumps did I say ELECTRIC = Voltage - you have VOLTAGE DROP(S) thru the PCM. What turns on the electric FUEL PUMPS ? I will give you 3 guesses.

THIRD and final time, POST # 86 has your possible fix. Please read it. Keep on playing with it, summer is almost over and you will be seeing snow very soon. Then it will be time to play with the snowmobile.

Trying to be funny here but you have 16 different ignition coils here to play with so you mean you can not change out 5 & 7 and possible 3 &1 on you lunch eater engine - port side. Find 8 good ones and use them - coils - plug wires - boots and spark plugs.. Also any wiring around or under the PCM not shorted out -check that as well. If you ever get this fixed by whomever please tell us what the complete fix was. Thank you and good luck.