Raylar

Merc has never really licensed anyone to do PCM555 program changes, they did collect fees from Whipple to unlock source codes on the PCM555's for a while and Whipple would pay a fee for each ECM they were given the program to reprogram. Mercury does not now even own the company anymore that built the PCM555 and developed the programs and programming for them- Mototron. With full data logging our programmer was able to build new re-flash programs for the various 496 packages we offer and build for the various versions of the 496 and we now use this re-programming of various year and model versions of the PCM555 that has been used for the 496 and the HP525efi.
As I mentioned we also leave the Guardian portion of the programs operational even after reprogramming so as to keep the engine protection that was developed by Mercury.
Mercury now uses a new ECM system on their new 2010 and 2011 engines such as the new HO502efi emissions engines, various outboard and inboard engines alike, most likely a case of additional emissions controls program size and power and the fact that a few like us have been able to now re-program the PCM555 which I am sure Mercury does not like for their control loss and exclusivity uses.

As for the forged GM crankshafts versus cast crankshafts in these engines we have never seen a major failure in either crankshaft from power overload even in supercharged versions of 750-800HP and the only crank failures we've seen and heard of the front snout of the crankshaft broke off from excessive supercharger belt tension.

As for the 496-8.1L engine stock components and cams, all marine engine companies as Mercury, Volvo, Crusader, Indmar, Marine Power, etc., GM Powertrain supplied all the 496's in two versions to all the marinizers, the HP1 -370-385 version depending on particular company programing and advertising as well as the the same for the HP2 420-425HP version. Except for the early 2000-2001 HP2 versions which a certain few had a forged crankshaft all these engines have been pretty much identical with a very strong nodular iron pressure rolled fillet cast crankshafts, forged I-beam not so strong connecting rods and all with cast hyper-eutectic pistons, press pin fit in 2000 thru 2004 and full float pin on 2004-1/2 thru 2010 engines. Only two camshafts have been used the truck camshaft rated at 375-385 horsepower in the marine HP1 engines and the 420-425HP version camshaft used in the HP2 engines. Everything else supplied by GM in these 496 8.1L engines is identical regardless of who marinized the engine for sale.

Best Regards,
Ray @ Raylar

Rage

So you have erased all Merc programing from the PCM555 and installed a different ECU programing language that you can reprogram but have included the 'Guardian' features?

Rage

The Merc 496 knock sensors only produce a voltage in response to vibration. Since there is always vibration in an engine there is always voltage coming out of these knock sensors. The PCM555 is programed (calibrated) to 'decide' when a 'knock event' is occuring and respond by retarding timing. Unlike the MEFI type ECU which does have a 'knock event' output that can be accessed/observed the PCM555 as Merc's is set up does not. I have data logged knock sensor voltage output and PCM555 real time ignition timing. I am told that the PCM555 timing out put that can be observed via Diacom is only that of the lookup table and not the actual timing.

macjazzy

Thanks for all the input from the various contributors of this thread. It has been very informative. There are a ton of these motors out there and for the most part they seem anvil reliable.

And for those of us with the lower rated motors, it seems like one the few engines that for a reasonable amount you could see real gains in power without really losing any reliability.

I am referring to the cam swap/ecm reprogram exhaust job.

Especially if one shopped around for some used parts, ie low hour cams out of 425hp's ( correct me if I am wrong, but a full roller cam like these should be fine to re reused from an engine that say....froze and cracked the block, or developed a knock etc....)

Also finding a used 425hp ecu should save a bunch of money, being as how many of these engiens are out there, it would just require a bit of leg work to find these parts. Then Buy the Dana exhaust ( which seems to be the hands down preferred favorite, if I am reading this thread correctly).

If you are capable of some basic do it yourself wrenching, this job could conceivably be done for 3-4k per engine including new exhaust, and possilby less is you got a real steal on used parts.

4k and you gain possibly 75hp, reliably, without real risk to the longevity, or drivebility on your engines. (Somewhere in this thread it was said an engine dynoed at 455 after these mods)

In the marine world I think that is a pretty good deal, now the big issue becomes, will that kind of increase make a difference in our individual boats.

Some boats would wake right up with an extra 75 -150 (twin engine) hp, some that may not make much difference. That is the big decision I have been debating in my situation for awhile. I am not sure that would make a real appreciable gain in my boat.

But I soooooo want to try!!! I guess I will just keep a look out for a couple of used cams, and ecu's

paul buckner

Hi RAY allways read all your posts and i am allways imprest with the amount of time you spend explaining things to people if i ever want more power from my 2x 496 ho, I will come to you for the parts Just read your last and you say some early 496ho 2001-2002 may have forged cranks ,is there any way you can tell from ser# i could not get my head down in the engine compartment to read the ser# so i pulled the metal tag off the block and it reads MO84566 ?? wot can you tell from this # .Mr Gaget who allso arnswers all Q is doing my bravo ones steel tower and top cap and blue printing so i may be ready for a motor upgrade soon .pistons rods sounds like a must then wotever you recomend 500hp is where i would like to be and if pos keep stock exhaust?? any im would be great best regards paul

Rage

Discussion on knock sensors by the experts:

http://www.offshoreonly.com/forums/g...systems-2.html

SDFever

In response to what you're "told"... There is no way for me to really understand what happened as a third party in conversation.

However, the timing you see in Diacom is the same timing I see in the CDS so if it isn't accurate then someone is playing tricks on the Merc Techs who are also part of their warranty program.

Consequently, we've used that same number as a means in part for further tuning. The fact that the dampeners have no marks and you have no way of putting a light on it (particuarly when it bounces negative) is certainly subject to some interpretation but regardless of what someone else says..

The computer must know real timing in order to maintain, stay alive, idle etc.

If there is a reference table "hiding" something from you while you're looking at it, that's a good topic for discussion but I do know for fact that when you adjust too high using the same numbers that you see in every day big blocks, it gets dangerous around 38. At least mine did on experimentation but every setup can be different.

Does it start at zero? Does it begin at about 6? I'm not sure but all the same numbers apply in my testing which means that I have no real reason to be concerned about different numbers buried at those sub-levels.

Respectfully, we can all find someone to tell us anything. Question is: does it apply or have any meaning that we need to be concerned with?

I can tell you exactly how your computer goes about putting all this on your screen but it would be terribly boring for most people.

Put your boat on plane at about 3100 and smack the block with a brass hammer...

Rage

What I tried to relay was that the Diacom read out of the engine ignition timing may not include the amount that the timing is retarded during a 'detonation event'. That is all.

My interest in this is because I am looking for a means to identify a 'detonation event' from available data.

SDFever

I see. You could record the data while running, save it, and go back to review it with the drag bar to try and find any pull back on the number.. I don't know if it would be there or it might occur so fast you can't see it with a scanner. I'm pretty sure the refresh rate of the CDS is far better than Diacom but that doesn't mean one would necessarily catch it still.

To be honest, I don't recall ever being able to do that myself. It's my belief that the oem knock system on that engine WILL let it destroy itself before you would ever catch it.

That's based on my testing that we did when I was really into programming.. I've never put any trust into that scenario.

Rage

I just asked Dustin about this. He advised that spark advance will not show (via Diacom/Merc diagnostic feed) if its retarding because its doing it per cylinder every firing so they just give you a generic, commanded timing. I will be installing a KnockLite to hopefully give some warning if things go wrong.