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  1. #1
    Platinum Member Platinum Member kubcat's Avatar
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    525hp marine 496 from GM

    I came across this engine on Ebay.

    http://cgi.ebay.com.au/ws/eBayISAPI....0%3D%26fvi%3D1

    It says it is a HP3 8.1 that produces 525hp.

    Googling it I came up with a few articles about 2002/03 and that it was used in boat racing.

    Apparently a HP1 is a 375hp, a HP2 is a 425hp and this HP3 is a 525hp. They are all based on the Vortech 8.1 or 496.

    http://media.gm.com/news/releases/021123_marine.html

    http://media.gm.com/news/releases/021126_apba_2.html

    They then seemed to have disappeared.

    Does anyone know anything about it especially the differences between a 425hp and this one?

  2. #2
    Gold Member Gold Member Rage's Avatar
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    I know quite a lot about the HP3 engine. Dave Stiff at Innovation Marine (941-355-7852) does as well though most of the people there that worked on the HP3 project are gone. Last I heard Innovation still had a stock pile of the original 87 octane HP3 engines on the shelf though that GM supported race program is long defunct.

    I basically attempted to convert a 2004 Mercruiser 496HO (425hp @ 5200 rpm on 87 octane) to a HP3.

    What specifically do you want to know about the HP3?

    Bill

  3. #3
    Platinum Member Platinum Member kubcat's Avatar
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    Quote Originally Posted by Rage View Post
    I know quite a lot about the HP3 engine. Dave Stiff at Innovation Marine (941-355-7852) does as well though most of the people there that worked on the HP3 project are gone. Last I heard Innovation still had a stock pile of the original 87 octane HP3 engines on the shelf though that GM supported race program is long defunct.

    I basically attempted to convert a 2004 Mercruiser 496HO (425hp @ 5200 rpm on 87 octane) to a HP3.

    What specifically do you want to know about the HP3?

    Bill
    Just wondering why they are not around anymore. An extra 100hp sounds like a good idea and I would love to bump up my 425's if feasible.

    Just reading the blurb, seems if we bump up the fuel pressure, change camshafts and exhaust and a reprogram we should get there.

  4. #4
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    Wink How to get 525HP from a 496?

    Kubcat:

    The old HP3 was a special engine re-worked by Innovation in Florida. It was never put into GM high performance as an available engine for reasons I won't go into here as we don't have enough time and space to go over the whole fiasco!

    If some one has an original for sale it will make 525HP with headers only and it has a very rough idle from a big cam design, can you say "reversion".

    If you want a more reasonable option visit our website @ www.raylarengine.com.

    Best Regards,
    Ray @ Raylar

  5. #5
    Registered jayhawk261's Avatar
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    Marine Power Service sells them. They are listed as the "GMB496HO+" and it says call for pricing & availability. They used to have a picture of them on their website and they were priced at about $15k. Link Below:

    http://www.marinepowerservice.com/Bo...roductID=24815

  6. #6
    Gold Member Gold Member Rage's Avatar
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    The HP3 differences from 496HO includes: custom ported heads (iron), GM ECU/sensors and programing with increased rev limit to 5400 rpm, Crane roller rockers, Crane roller lifters, Trend high strength push rods, custom Crane cam (I have a HP3 cam if you are interested), CompCam Nascar valve springs and hardware, high volume oil pump, Coyle timing sproket, fuel pressure set to 58 psi (on Mercruiser conversion you have to add an adjustable fuel pressure regulator). The original HP3's also had the stock intake manifolds Extrude Honed to improve flow somewhat. In race trim they are set up with CMI's. With stock Mercruiser 496HO exhaust instead of the CMI's subtract about 30 hp even with the turbulators removed and the exhaust manifolds ported. My stock manifolds have since been replaced with with Dana Torque Flow exhausts that reportedly come very close to the CMI's performance.

    In my opinion the Nascar springs are over kill and not really necessary since the cam is not that radical plus their higher preload is harder on the valve train. If you use the Nascar springs you better use the Crane roller lifters as well.

    The finalized HP3 as described above is extremely robust. One unit is still being campained after numerous seasons with no issues.

    The one thing about the HP3 that is unnerving is the extremely close PV clearance of ~0.028" from the HP3 Crane cam's increased lift and duration. That is why GM opted for the Nascar springs. The combination works but I opted to cut the intake valve piston relief deeper in the stock pistons and use lighter valve springs and stock roller lifters. This additional thinning of the stock Hyper Eutectic cast aluminum piston top is probably not the best idea if one intends to consistently run the engine hard.

    The 496HO was successfully converted to a ~HP3 w/o the CMI's, Nascar springs, Crane roller lifters, GM ECU, Coyle sproket or HV oil pump. The Mercruiser PCM555 ECU was reprogramed to 5400 rpm rev limit by Dustin Whipple with recorded A/F, MAP, TPS and RPM data provided by Innovate Technologies LM-1 A/F meter/data logger and LM-2 RPM converter/data logger cable. The 43 psi stock fuel pressure was increased to 50 psi which produced A/F that was pretty much dead on throughout the rpm range.

    The HP3 race engine program was apparently shut down by GM do to Mercury's displeasure with GM's competing with them in the marine engine/racing engine market. Some hard ball being played with the race teams is also plausable. Seemingly a GM business discision to get out.

    Parts are available from Innovation Marine and complete HP3 engines as long as the stock lasts.

    Quote Originally Posted by kubcat View Post
    Just wondering why they are not around anymore. An extra 100hp sounds like a good idea and I would love to bump up my 425's if feasible.

    Just reading the blurb, seems if we bump up the fuel pressure, change camshafts and exhaust and a reprogram we should get there.

  7. #7
    Gold Member Gold Member Rage's Avatar
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    ADDENDUM:

    I neglected to mention that the stock Merc 496HO valve springs were replaced in my setup based on the HP3 Crane Cam timing card, but not the Nascar springs which are significantly higher load.

    My simulated HP3 converted 496HO ran flawlessly for one season/90 hours with zero reversion issues. The HP3 idle is to my ears wonderfully robust sounding but completely docile relative to driveability and remained at the stock 650 rpm. However with the stock Merc exhaust manifolds mine was not at the full 525hp potential so I moved on.

    Knowing what I know now and if I wanted a NA 525hp or 627hp upgrade to a Merc 496, I would go with the Raylar HO525 or HO600 packages.

  8. #8
    Platinum Member Platinum Member kubcat's Avatar
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    Quote Originally Posted by Rage View Post
    The HP3 differences from 496HO includes: custom ported heads (iron), GM ECU/sensors and programing with increased rev limit to 5400 rpm, Crane roller rockers, Crane roller lifters, Trend high strength push rods, custom Crane cam (I have a HP3 cam if you are interested), CompCam Nascar valve springs and hardware, high volume oil pump, Coyle timing sproket, fuel pressure set to 58 psi (on Mercruiser conversion you have to add an adjustable fuel pressure regulator). The original HP3's also had the stock intake manifolds Extrude Honed to improve flow somewhat. In race trim they are set up with CMI's. With stock Mercruiser 496HO exhaust instead of the CMI's subtract about 30 hp even with the turbulators removed and the exhaust manifolds ported. My stock manifolds have since been replaced with with Dana Torque Flow exhausts that reportedly come very close to the CMI's performance.

    In my opinion the Nascar springs are over kill and not really necessary since the cam is not that radical plus their higher preload is harder on the valve train. If you use the Nascar springs you better use the Crane roller lifters as well.

    The finalized HP3 as described above is extremely robust. One unit is still being campained after numerous seasons with no issues.

    The one thing about the HP3 that is unnerving is the extremely close PV clearance of ~0.028" from the HP3 Crane cam's increased lift and duration. That is why GM opted for the Nascar springs. The combination works but I opted to cut the intake valve piston relief deeper in the stock pistons and use lighter valve springs and stock roller lifters. This additional thinning of the stock Hyper Eutectic cast aluminum piston top is probably not the best idea if one intends to consistently run the engine hard.

    The 496HO was successfully converted to a ~HP3 w/o the CMI's, Nascar springs, Crane roller lifters, GM ECU, Coyle sproket or HV oil pump. The Mercruiser PCM555 ECU was reprogramed to 5400 rpm rev limit by Dustin Whipple with recorded A/F, MAP, TPS and RPM data provided by Innovate Technologies LM-1 A/F meter/data logger and LM-2 RPM converter/data logger cable. The 43 psi stock fuel pressure was increased to 50 psi which produced A/F that was pretty much dead on throughout the rpm range.

    The HP3 race engine program was apparently shut down by GM do to Mercury's displeasure with GM's competing with them in the marine engine/racing engine market. Some hard ball being played with the race teams is also plausable. Seemingly a GM business discision to get out.

    Parts are available from Innovation Marine and complete HP3 engines as long as the stock lasts.
    Wow, this is why I love OSO. Rage, you really know your stuff.

    I tend to agree that it appears Mercruiser being such a huge customer wouldn't want competition from its supplier and I guess Mercruiser already have a 525hp that they have pitched at a higher price/quality.

    Seems like Raylar has taken over development where GM stopped.

  9. #9
    Gold Member Gold Member Rage's Avatar
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    GM started out trying to keep the 496 as close to stock as possible so that they could not only keep production costs and therefore price down but also market it as their "Truck Engine" that could compete with race engines. In other words both their truck division as well as there marine division would benefit from the exposure. That worked with 87 octane versus the Merc 500 but not the 525. The Gen II HP3 to compete with the Merc EFI525 was going to be a 560+hp engine on 87 octane. They got as far as the dyno durability test and one of the hyperuetectic cast aluminum pistons let go. At that point the politics previously noted seemingly convinced GM to bow out. Innovation Marine continued the engine R&D program on their own for a while but the deep GM pockets were gone and Mercury I suspect was no less aggressive in working to squelsh Innovation's race engine efforts. Say..........800 pound gorilla. The Innovation engine was renamed the HI engine designation and retained the stock intake but went to forged pistons, some slight additional compression, a bigger cam, 5600 rpm, 93 octane and more advance. Baseline was about 575hp fully broken in. That was with the stock 496 valves, 2.195" intake and 1.72" exhaust. When Jim Valako added 2.25" intakes and 1.84" exhaust his porting magic and bore notched the cylinders they were getting close to 600hp, still with the stock intake (but always CMI's). I am not sure if they ever campaigned the JV modified heads noted.

    GM seems to have wanted to make a marketing point that their truck engine was also as good/durable as a race engine. If they wanted to make a real race engine I think no one would doubt that they could. No doubt having their race engine being compared as no better a preformer than a GM truck engine was grating to Merc.

    Power politics.

    The Raylar heads and the Raylar intake are hugely better performers than the stock units in my laymans opinion and all those more knowledgable that I take guidance from. With the bigger valves and JV's porting and bore notching the iron heads would seem to be comparable to the Raylar heads (with the standard size valve heads but smaller 11/32" stems) at least in the CFM department. Burn efficiency is likely still better with the Raylar heads based on the lean A/F they seem to be able to run at.

    I cast my lot (and money) early on with the HP3 heads and for better or worse that is where I stay. Again, I would choose the Raylar heads next time for the 496.

    Quote Originally Posted by kubcat View Post
    Wow, this is why I love OSO. Rage, you really know your stuff.

    I tend to agree that it appears Mercruiser being such a huge customer wouldn't want competition from its supplier and I guess Mercruiser already have a 525hp that they have pitched at a higher price/quality.

    Seems like Raylar has taken over development where GM stopped.

  10. #10
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    I still never got the resistance GM has for running forged pistons in their newer engines
    (LS1/2/etc and 8.1s) instead going for the Hyperpathetics.
    First thing everyone is forced to do when making real power in a newer LSx or 496 engine whether car or boat is take the damn thing apart and get some real pistons.


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