454 "Crate" HO to Marine

Discussion in 'DIY Marinizing' started by Eric G, Jul 10, 2005.

  1. Eric G
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    Eric G New Member

    I recently toasted my 454 in my boat. It was a factory installed 454 Mercruiser w/330hp with a Bravo 1 outdrive . I am looking to replace the motor with a 454 H.O 'crate ' motor from Jeg's Performance. The motor I am looking at is a 454 w/425 HP@5250 RPM and 500 ft. lbs @ 3250 RPM. The motor is a Gen IV block with forged steel crank, windage tray, forged pistons, forged shotpeened rods, four bolt mains and a Hydraulic Roller cam Lift .510 int./ .540 exh, Duration@ .050" 211 int/ 230 exh. I will use the marine starter, altenator, exaust and fuel pump off my existing motor. I will also change the freeze plugs to brass. My question is will this motor work? Are the head and intake gaskets ok. I will need a new carb. Will a regular carb work or do I have to use a marine application? Your help and comments are appreciated.
     
  2. marshmat
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    marshmat Senior Member

    Sounds like you've already read the book and are doing it right. I see no reason to suspect your motor won't work. (Although I do suspect it will not be long-lived; high-output tuned-to-the-limit motors never are.) As far as I know marine and automotive gaskets are identical; the carb is also interchangeable. You will need a marine flame arrestor for the carb intake, in place of the automotive air filter. Brass freezeplugs and marine-grade starter/alternator/pump are good ideas. Also take a look at the cooling systems to make sure they are compatible; the car and boat ones are sometimes different but it's an easy change. With the aggressive cam and high-performance innards giving a substantial power boost over the old motor, you will also need a steeper prop. Make friends with your local prop shop and they'll let you test-drive a few wheels to see what works best.
     
  3. gonzo
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    gonzo Senior Member

    That camshaft will probably not work. It is for a different application. The gaskets, unless they have stainless core, need to be changed. The intake manifold needs a bronze insert in the water bypass. Marine carburators have the overflow pipe into the inside of the primaries instead of the outside. Marine circulation pumps have stainless shafts and seal springs. Marine engines use high flow/ std.pressure oil pumps because they usually run at high RPM for extended periods. The oil pan and oil pickup need to be for the right installation angle. Automotive pans are usually too shallow for marine use.
     
  4. Jango
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    Jango Senior Enthusiast

    The "Bottom End" of the 454 HO crate motor is substantially beefier than your old motor and built for sustained high RPM's. I would be supprised if it already doesn't have a High Volumn Oil pump. Like the marine version (which is basically a Truck Engine with marine externals) Prop your Boat for max. RPM,s near the max. power Band, or 5200 - 5400 RPM's for the crate engine. Both Ford and GM Marine camshafts have the same specs as their Truck cams. The crate engine cam is Healthier, but fairly mild with a good torque band and should work well.

    My 5.7, 270HP Mercruiser used Copper Clad Head gaskets which appeared the same as Automotive type - no sign of Stainlees Steel. Unless your Boat is only operated in Salt water (without closed cooling) I would think Std. gaskets would be addequate. My Mercruiser is operated in the same water that comes out of the kitchen sink in my home.

    I also have a 20' Inboard powered by a 302 Ford Mercruiser which has been altered to produce 380HP. This is my third year with this 75 mph Boat and the motor is fine. If the motor is built right you shouldn't have problems.
     
  5. SOB
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    SOB Junior Member

    What about reversion? How is a cam selected to prevent it?
     
  6. gonzo
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    gonzo Senior Member

    Use a cam that is rated marine. It will be appropiate for the installation. If you are hotrodding though, it is different. The whole setup should be designed as a unit. There are no best components. It depends on the rest.

    Jango:
    Marine exhaust manifolds use stainless inserts. Automotive have steel inserts that rust and leak.
     
  7. Jango
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    Jango Senior Enthusiast

    Thanks Gonzo,
    I realize Marine Exhaust Manifolds are totally different than Automotive. Automotive types are not water cooled either. WOW, what a fire haszard!

    If you are really talking about Intake manifolds, the Intake manifolds on my Boats are Aluminum (fresh water use)

    Also this is a General Motors manf. motor with ALL GM parts. I would assume with "matching parts"

    Jango
     
    Last edited: Sep 12, 2005
  8. gonzo
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    gonzo Senior Member

    GM has a division that puts together marine engines. Both VolvoPenta and Mercruiser get the long blocks assembled to their specifications.
     
  9. stonebreaker
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    stonebreaker Senior Member

    Well, I'm nine months late, but considering that the 454 HO's got well over 400 ft lbs of torque below 1750 rpm, I seriously doubt he's going to be lacking for low end grunt.

    http://www.gmgoodwrench.com/perfparts/images/parts/pdf/12568774.pdf

    In addition, the cam in the 454 HO is a hydraulic roller - a substantial improvement over the old flat tappet type in the mercruiser engine.

    Also, the 454 HO has the rectangular port heads - much better than the oval port heads on the mercruiser engine.
     
  10. gonzo
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    gonzo Senior Member

    The 454 HO is available marinized by several companies. It has had square ports for many years now. Unfortunately GM discontinued it and replaced it with the 8.1. which is having a high failure rate in marine applications. I don't know what is happening in trucks.
     
  11. Ike
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    Ike Senior Member

    Marine carbs are not the same as automotive carbs. Marine carbs are designed to prevent fuel from leaking from the carb into the boat, so any leak such as a stuck float or leaky acceleration pump will go down the carb throat, not out onto the engine. Marine carbs also tend to be jetted differently and built heavier. Outwardly they look exactly the same so it's hard to tell if it's a marine carb just be looking. You need make sure you look for the right model.

    Here's the catch, since they are made in much lower volumes than automotive carbs they cost a lot more. Yes, they are required.

    The exception. If this is one of those boats where the engine is out in the open air, then you can get away without a marine carb and not violate any safety standards. However if it's in a enclosed compartment you need a marine carb.
     
  12. stonebreaker
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    stonebreaker Senior Member

    :confused: GM still makes that motor. Maybe you were thinking of Mercury?

    I would imagine the problem with the new 496 is it has not caught on in automotive circles. Its heads and ignition system are based on the LS1's, so it has a lot of potential...but I'm not aware of a single hotrod application using one. Even GM Performance Parts, although it carries supercharged versions of the 3.8 liter V6 and even the 4 cyl Ecotec, doesn't offer anything for the 8.1 vortec engine.

    The traditional GM smallblock made some fairly serious compromises in the airflow department, and so it's worth spending the big bucks to hop up your LS1/LS2. However, the big block was originally conceived as a race engine, and its horsepower potential is just about as good as anything out there, even 40 years later. Therefore, it's really not cost-effective to buy the 8.1 vortec for a performance application - traditional big block parts are just too cheap and too good for it to compete. Hell, did you know you can buy a 620 hp crate motor straight from GM? It costs 13 grand, but it's SAE rated for 620 hp and runs on 92 octane. Anyway, with that kind of competition out there, I think the 8.1 just isn't going to make it as a perforance engine.
     
  13. matthewfnorbert
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    matthewfnorbert Junior Member

    .

    yeah you could go the 572 620 horse or why not fit the new Ls2 400hp with injection, would cost around 9k for motor, loom and ecu plus any bell housing required and change cooling system connections to suit. most crate motors go very well in boats esp the ZZ series...
     
  14. stonebreaker
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    stonebreaker Senior Member

    I was browing through the Summit Racing catalog while I was making a, er, 'pit stop' this morning, and came across a very interesting crate motor candidate. World Products has a 454 ci crate motor...based on a smallblock. I see two advantages to the smallblock version: It's about 250 pounds lighter than the big block version, and because the smallblock achieves its displacement with a longer stroke and smaller bore than the big block, it should have slightly better fuel economy at low speeds.

    The short block's pretty expensive, nearly five grand, but is fully race-prepped - the block is CNC machined, has splayed 4-bolt billet steel main caps, and the rotating assembly's completely forged. The complete crate motor version of this engine sells for about eleven thousand, and generates 600 hp and 605 ft/lbs of torque...with cast iron heads, no less.

    Not exactly cost-effective for a runabout, but definitely fun to think about.
     

  15. gonzo
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    gonzo Senior Member

    The high performance engine builders have used big blocks to make a 350. It is the only way to make them stay together. The HP rating of this "high performance" or "racing" automotive engines is not for continuous use. Marine service puts the engine at full torque for long periods. Bearings are designed for different services. They are of alloys and combinations that have the best hardness and flexibility for the application. Other engines will work, but if you are spending so much money it may end up being an expensive experiment.
     
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