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

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?

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.

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 from England
 

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

Discussion on knock sensors by the experts:

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

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...

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.

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.

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.

That is my undersdanding as well. If the engine is set up such that it will inherantly want to detonate the Merc knock control system will not protect it. Sounds like this system would: http://www.jandssafeguard.com/safeguard.html

Rage, I don't doubt for a second whether or not you're a sharp guy. I'm sure you're probably much sharper than I am.

In all honesty, I think you are SERIOUSLY splitting hairs that in the end won't net much.

You can study a text book on law and know all or most of the answers but most people still need the attorney to show in court. Often times, the experience prevents the attorney from having to go back and read the book again. You can put every single warning alarm on your engine and still screw it up. That goes for all of us.

If the engine is setup and run properly, there is no need to do this. For that matter, nothing lasts forever obviously and if it matters that much one could always park the boat and never use it.

Question is: how far to take the worry? It's all just junk waiting to break no matter what product you buy or who you buy it from. Detonation happens when things aren't done properly.

To try and tie this into a 555 is overkill.

You fix it and move on. It's just one mans opinion. :evilb:

The J&S Safeguard would be over kill for me. There are no plans to do that. The KnockLite that I already have will be installed mostly as a back up to watch over my baby. I am now retired and have way too much time on my hands and much less mad money than before to fix expensive things when they break. Also I love this stuff as a hobby.

We do have different philosophys but we both love to run them hard and fast.:evilb::evilb::evilb::evilb::evilb::evilb:

Ok, I figured I would post in this thread rather than start a new one since there are many on this subject. I have been contemplating doing the MAG to HO conversion and have pretty much changed my mind a hundred times. My 32 Advantage, with twin 496 runs fine around mid 70s. I realize that the approximate 100 hp will not affect speed much at all but it surely won't hurt and they just sound better. I already know the price, and know who I would have do it. About a month ago, I was convinced and was planning on the trip to take the boat. Now, with talk of gas at $5 a gallon, I am faultering on my commitment. The roughly $5K it is gonna cost will buy quite a bit of gas. I think I already had the GF sold on the idea by telling her that it would "raise the resale value of the boat if we wanted to sell since they are will still be technically stock". I bought the boat summer before last at a repo seller, and it showed 44 hours. (not sure I believe it though) The boat sat for a while, and the engines look brand new, but the outdrives look a little more worn (not bad though). Anyway, I figured since my builder would already have the engines out, he could scan each motor for a realistic run time(they show 71 now), and also check them out to make sure they are in good shape even though they ran like tops last summer. I went and re-read this whole thread and opinions run from "Don't waste the time or money" to "Best upgrade for the buck available on the 496". Just trying to re-convince myself.

If you can do the work all yourself it's not a bad deal. If you can not, it's not a good deal.

I won't attempt the work myself, I could PROBABLY do it, but having a professional do it would be MUCH cheaper....And I would get to use the boat THIS summer. LOL!

Scan the motors while they are in the boat and if the numbers match your meters leave it alone and put that money in the tank and enjoy the summer boating!

someone has the HO cam spec?

Don't forget you'll be doing a stage 1 Whipple reprogram so you'll be getting an extra 5-10 hp out of the deal. Plus a very noticeable low end torque improvement due to a more aggressive timing curve in the PCM. Let's see, you will also get a huge fuel mileage improvement....well, maybe not. LOL But it's a good selling point:evilb:

My last statement got me to thinking, so I went back and pulled up some prop shaft dyno tests I've done. Interesting comparison. At 3000 RPM the 496 Mag made 445 Ft. Lbs of torque, the HO made 448 and the stage 1 HO made 479. That is a 30 ft. lb. increase over the stock HO program at the critical planing rpm and the gains carried all the way to 5100 RPM, where the stage 1 made 410 pshp and the stock HO made 395, the Mag made 351 hp @ 4700. Anyway, just more stuff to think about. Carry on...


Bob Lloyd
Full Throttle Marine

JMO, but I definitly think the +100 HP add to your 32 foot boat will definitly translate into what should be a 7-10MPH increase in speed and a considerably improved mid range acceleration and a lower rpm cruise speed which could net some fuel savings while still being able to run 87-89 octane fuel with the right reprogram on the ECM. At $5k that tranlates to about $50 per horsepower and in todays high performance marine world that ain't bad by any stretch. If you had bought the boat new with HO's the damage would have set you back somewhere between $9K-$12K with most builders. If and when you sell the boat I would definitly think the $5K will come back in the buyer who wants the HO's or better.

Best Regards,
Ray @ Raylar

If Bob L. is doing the work and you are doing the Whipple upgrades all for $5K for both motors then ignore my previous post and go for it!

Well, I think you guys have pretty much sold me! Ray, the speed you talk of sounds great! Just not sure how this big hull will react to more HP. My only concern is will this upgrade affect the reliability of these engines? I realize that even stock stuff breaks, I just can't at this point justify another $10K to fix one of these things. I just won't mention that to Paula (GF).:party-smiley-004: I'm having a snap on cockpit cover made next week, and getting new tires on the truck as well to prepare for the trip. Bob, as soon as I can lock down a date to come down, I will let you know. I'm trying to get this thing started before your spring rush begins (which may have already started) Oh yeah, Bob, Loren has been REALLY selling me on this trip as well. Thanks guys, I knew I could count on you to help me "decide"....:thankyouthankyou:

I measured one several years ago. I came out to 222/236 duration @ .050 and .496/.510 lift. LSA is around 116 the best I could calculate. Raylars 103 cam has a bit more lift and quite a bit more intake duration. He may chime in with specifics if he desires.

Bob Lloyd
Full Throttle Marine

If I remember correctly your boat runs right at 70. A 100 HP increase would put it around 74-75 under the same conditions.

Me and Loren have seen 74 on GPS. Not EVEN gonna try to get to you and Marc's level though!

As long as Whipple doesn't raise the rev limiter to some crazy RPM and you don't run with the throttles in the kitchen all day long your reliability should not be affected.

Where's the Limit?
 

I would like to comment here on the rev-limiter on stock 496's.
The valve springs (a bit light) and the heavy 3/8" stem stock steel valves in the stock iron heads definitly should have a rev-limit of about 5200 rpms max. for good reliability. When you upgrade a 496Mag to HO, the heads, block, etc. are all the same and the HO comes from Mercury with a 5150 rpm rev-limit which is good and safe as a rev-limit. Taking these stock valve train components above that 5150-5200 rpm limit is not really a smart thing to do unless the ECM reporgrammer is going to warranty your engine. If you upgrade your valve springs and retainers and such as many of our customers have done running our aluminjum heads then running the engine up to 5300-5500 rpms is much safer but as with any high performance engine when you push the RPM limits up you can lessen reliability especially if you tend to use a fair amount of high rpm usage and you stay at WOT for longer periods.
Just my fairly expierenced opinion.

Best Regards,
Ray @ Raylar

I'll have to try to keep them no farther than the laundry room! Besides, if I keep em in the kitchen too long, I'll be in the doghouse!(and poorhouse) Bob said the limiter would be set at 5100, which I don't think I will have to worry about with the 28s.

Thanks Ray, that is pretty much what Bob told me.

Well I don't know if you can gain performance from just a PCM reflash, but you can sure lose it. I have an early 2001 496 mag (#OMO61519) and I wanted to install a Mercmonitor on the boat. Mercury said that I had to have the PCM modified for this to work. I was skeptical of this since a scanner showed all the engine information was available, but Mercury built it and they should know. The reflash was free and part of a recall (Fix Campaign 2001-014).

Unfortunately I did not seem to get just a reflash, but a different PCM. Equally unfortunate is that I do not have the serial number from the original PCM as that may be of interest to this thread. In any event the different PCM no longer soots the transom up like my old one did, and it does provide a small improvement in fuel consumption, but I also lost 4 mph. No other running changes were made to the boat at this time.

Since the acknolowdged experts on the 496 seem to be following this thread, I thought I might fish for comments and satisfy my curiosity. Clearly if there are performance reductions in a "newer" programing spec, there might be performance enhancements available by reverting to an older specification.

Ray and others, does this make any sense to you and would you be willing to share your general knowledge of what programing changes Mercury may have made through the years?

Thanks,

Dan

I've run them to higher rpm than stock, but the power drops rapidly past 5100 rpm so there really is no point in raising the rev limit. Peak HP with the stage 1 program was 5000 rpm. Even the Raylar 103 kits peak around 5200.

The Raylar 103 pkg is designed to run at 5350 (Raylar's recommendation) and with the reprogram the limiter is set at 5450.

I had Whipple do a Stage II Flash on my 496 Mag (non-h.o.) last summer. THe main reason I had it done, is my 2001 496 mag produced way too much soot on the transom. While Merc was willing to flash for free, I opted to have Whipple to it because I would only be down for 3 days, where Merc wouldn't give me a time frame...... Anyway back to the STage II flash. THis also included a much cooler T-Stat and now the use of premium fuels. The overall speed gains were maybe 1-2 mph, but the MAJOR gain was in torque. My Velocity 260 now pops up on plain effortlessly with the Stage II flash compared to the Stock Merc Flash. That right there made it worth the $$ for the Flash. Plus the idle is completly different. It has a much more agressive sound at idle....

My dyno testing shows the peak power at 5200 and it starts dropping after that. I guess you can run it higher but it won't make more power.

Awesome thread. This question was asked earlier but I didn't see a responce. For someone doing the mag to ho upgrade would it be better to run the stock ho cam or the 103 raylar cam? Not sure on the cost difference but wondering if it would be worth it.

No offense but there is conflicting info on this one. And I will assure anyone who raises the limit running OEM pistons that you will only break them (or one) sooner.

Ray has moved on this number a couple times possibly by pure accident; I don't know but I've noticed it.

In a constant rpm engine (marine) they should never be made to go any faster.

Since you got the new computer for free perhaps you can send to Whipple and try the stage 2 and hope for noticeable results.

If you were to even bother with thinking about the time and labor to remove cam, you may as well buy the Raylar Cam if only because the stock ones are so bad it's not worth the time to reinstall. What's $400 these days in boat parts?

Just my opinion.

Well, I've had the upgrade now for most of the summer and can happily report that it has been everything I expected and alot more! I can run a little over 5000rpms with the 28s and the low end torque is amazing! Picked up about 7mph to boot! They sound great and don't soot the transom anything like they did with the Mags. Perfect upgrade in my opinion!

Which upgrade?