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  • Marine 454 Big Block

    Hi Guys,
    This is my first post on Bangshift. I really dig this sight. I was having a discussion (or debate) with a friend of mine regarding the marine 454 big block engines (e.g. mercury mercruiser 454). We were wondering if a marine 454 like a mercruiser 454 can be swapped into a car. We were thinking swapping in a big block in my '70 Impala and he suggested to look into the marine big blocks. He thinks it is possible since the marine big block is derived from a passenger production big block chevy. My stance is I'm not sure since I have never seen one. Since I have never scene one I do not know if the mounting bosses/holes are different or match up with a production motor. Anyone here familiar with this? Thanks in advance.

    -Jesse

  • #2
    Re: Marine 454 Big Block

    yes you can.. you'll need to change the intake and exhaust manifolds. and maybe the water pump

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    • #3
      Re: Marine 454 Big Block

      Thanks Tazracing.

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      • #4
        Re: Marine 454 Big Block

        The long block is essentially the same. It's all the accessories that are different, intake, carb, exhaust, water pump and such.

        They are tough engines. They are designed to run at a higher rpm than ones in cars. My Uncle's big boat had twin 502 bbc Mercruisers and they ran at 4500 rpm while at cruising speed. No one runs a street car at that rpm very long.
        BS'er formally known as Rebeldryver

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        • #5
          Re: Marine 454 Big Block

          Originally posted by Rebeldryver
          They are tough engines. They are designed to run at a higher rpm than ones in cars. My Uncle's big boat had twin 502 bbc Mercruisers and they ran at 4500 rpm while at cruising speed. No one runs a street car at that rpm very long.
          what was redline?
          Si vis pacem, para bellum

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          • #6
            Re: Marine 454 Big Block

            Originally posted by kyhunter89
            Originally posted by Rebeldryver
            They are tough engines. They are designed to run at a higher rpm than ones in cars. My Uncle's big boat had twin 502 bbc Mercruisers and they ran at 4500 rpm while at cruising speed. No one runs a street car at that rpm very long.
            what was redline?
            Don't know. Tachs didn't show redline. I'm guessing around 6000.
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            • #7
              Re: Marine 454 Big Block

              they are the same as a forged 454 short block..
              they run at 4500 all day because there is a load on it.. water puts more of a load on it than a car does.
              in a car once you get to 4500 rpm in high gear. the engine sees almost no load.. compaired to getting the car to that speed , once it's there it takes nothing to keep it going,, in water, the load to keep the boat moving puts 90% more of a load on the engine than a car would..
              put a pass car 454 in an older bus sized motorhome and you can run it at 4500rpm all day if you want..
              lack of load is why running a car with a 454 at 4500 all day would kill it..
              boat castings might have more nickle in it as it has to deal with salt water, but alot of newer boats 1999 up run a closed cooling system (think car) over the older system of use'n salt water as the coolant and flowing it from the ocean then in engine then to ocean..
              good luck..

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              • #8
                Re: Marine 454 Big Block

                Marc is right, higher nickle content to help fight off corrosion from salt water, other than that, car/truck vs marine blocks are identical. The internals may be different for a boat application, but a lot of trucks were different from pass cars. I did a 305 sbc (Mercruiser) for a friend a few years ago, and that's what I found out on marine vs pass blocks.
                Whiskey for my men ... and beer for their horses!

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                • #9
                  Re: Marine 454 Big Block

                  I grew up in Fond du Lac, WI. My dad retired from Mercury Marine foundry a few years back.
                  15 years ago I was fortunate to see both the High Performance shop and the dyno labs. Seriously crazy sh!t in there.
                  I can tell you that there are a few very fast cars in the area that have black big blocks in 'em, and they are very, very fast ;D
                  So, yeah... they can be easily installed in a passanger car ;)

                  Look at the specs of some of the V8 marine engines, they make big horse power at low RPM's using low octane fuel, neat stuff. The test procedures are insane, I don't remember the details any more but I think it was a few hundred hours at full load/full throttle.

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                  • #10
                    Re: Marine 454 Big Block

                    Funy story, in about 1988 I was working on roof of Mercury Marine (Tar roofing, fun stuff) and I look over the efge and there is a DUMPSTER full of big-blocks! :o I nearly fainted.

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                    • #11
                      Re: Marine 454 Big Block

                      As stated - marine engines are pretty hard core - but they have one easy out - unlimited cooling capacity!

                      The open cooling system engines have no pressure to speak of to keep down localized boiling - so they run low temp thermostats around 160 usually - a "sea pump" pulls water out of the lake - pushes it to a manifold that distributes it full time to the water jacketed exhaust and only when the thermostat is open to the rest of the engine. All of the water exits through the exhuast. So you basically have an endless supply of low temperature water to pull from.

                      Higher end boats have closed cooling systems with a liquid to liquid heat exchanger that has lake water running through one side and engine coolant through the other.

                      The one thing to be leary of when buying a used marine engine is salt water damage intenally - some open cooling system boats run the salt water right through the engines - if they are not flushed with fresh water often - the resulting corrosion is horrifying.

                      I saw many aluminum intakes and heads completely destroyed from the inside out by salt water corrosion.

                      There's always something new to learn.

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                      • #12
                        Re: Marine 454 Big Block

                        That's a very good point, being so far away from salt water here in the midwest I hadn't thought of that. :D
                        I've seen the result of salt water on marine engines and some other equipment and it's crazy.
                        I wouldn't touch ANY marine engine that had salt water run through it directly.

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                        • #13
                          Re: Marine 454 Big Block

                          A big thanks to everybody! You guys have been very helpful and have given me good input. I have been seeing a bunch of boat big blocks for sale. And my guess buddy is right, I can use that engine if I find a decent one. I have been seeing a bunch of these for sale for a bit lower than a pass or truck big block but the asking price might reflect the condition (i.e. salt water rust as most of you guys have indicated). I truely appreciate your guys' help. I gues in the mean time i'll keep my eyes peeled.

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                          • #14
                            Re: Marine 454 Big Block

                            Originally posted by jesus
                            A big thanks to everybody! You guys have been very helpful and have given me good input. I have been seeing a bunch of boat big blocks for sale. And my guess buddy is right, I can use that engine if I find a decent one. I have been seeing a bunch of these for sale for a bit lower than a pass or truck big block but the asking price might reflect the condition (i.e. salt water rust as most of you guys have indicated). I truely appreciate your guys' help. I gues in the mean time i'll keep my eyes peeled.
                            I had a neighbor who bought a bought with a Ford 302 based I/O that spent it's life in the ocean. It snapped it's crank in half 30 minutes after he put in the water. Heads and intake look great, but the block and oil pan, which were hard to see in the boat, looked like they spent 20 years at the bottom of the Pacific.
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                            • #15
                              Re: Marine 454 Big Block

                              Hey rebeldryver, nice to see your '70 caprice in the forums. It's inspiring me to get mine up and running.

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