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difference between Auto and Marine engines

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  • difference between Auto and Marine engines

    I am planning a flywheel change, while the engine is out I am going to install a new engine, I was wondering what is the difference between a std Auto engine and a Marine app. I have the std rotation 5.7 2bbl holley. I have found the difference is hundreds of dollars and was wondering why.
    1996 22ft Chris Craft B/R
    5.7 Volvo Penta SX
    14.5 x 18 - SS 4 Blade Apollo


  • #2
    Re: difference between Auto and Marine engines

    I have found the difference is hundreds of dollars and was wondering why.
    Ayuh,...

    It depends on Exactly what you're comparing...
    Any Grease is Better,..... Than No Grease at All.......

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    • #3
      Re: difference between Auto and Marine engines

      I am planning on only changing out the short block and have the heads rebuilt, or the complete assembled long block. I am very familiar with Chevy engines (auto) and I was wondering if there was any difference between the Marine and Automotive versions.
      1996 22ft Chris Craft B/R
      5.7 Volvo Penta SX
      14.5 x 18 - SS 4 Blade Apollo

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      • #4
        Re: difference between Auto and Marine engines

        Originally posted by Bond-o View Post
        Ayuh,...

        It depends on Exactly what you're comparing...

        Especially if you are just looking at short or long blocks. The only notable difference in prices would be in the Marine peripherals like distributor, carb, starter, alternator and exhaust manifolds.

        You also may find a substandard bargain basement automotive rebuild that no one makes an equivalant marine one for. It's really all in the freeze plugs and cam for a short block and stainless steel head gaskets in the long block. Otherwize it would be the quality of other components and the quality of the machining and workmanship.
        For the time will come when men will not put up with sound doctrine. Instead, to suit their own desires, they will gather around them a great number of teachers to say what their itching ears want to hear. They will turn their ears away from the truth and turn aside to myths.-2 Timothy 4:3-4:

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        • #5
          Re: difference between Auto and Marine engines

          Other than the cam & the brass core plugs, the only difference should be the bolt on's, starter, etc.....
          You could get one out of the junkyard as long as it is from the same era....
          Disclaimer!: In my inexpert opinion......

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          • #6
            Re: difference between Auto and Marine engines

            Thanks for you help. With the price of a cam and core plugs I should just pay the extra and get an engine with a marine application, I plan on using all of the other bolt ons. Thanks again for your help
            1996 22ft Chris Craft B/R
            5.7 Volvo Penta SX
            14.5 x 18 - SS 4 Blade Apollo

            Comment



            • #7
              Re: difference between Auto and Marine engines

              I dont know where some of these fellows got there info but there is a big difference is a auto vs marine. The mechanicals are the same but camshaft is different so engine will not suck water into cylinders thru manifolds @ idle.(exhaust pulses) The internal clearances are different as the auto engines are set up to run at slower rpm due to transmission downshifting vs marine near max rpm operation. The is also one reason why Mercruiser specifys 20w40 or straight SAE 30 engine oils. Also the FC-W oils have a higher zinc content to reduce scuffing and wear. The auto oils have reduced or eliminated zinc to meet emissions and prevent O2 sensor failures. Thats why when you get a replacement engine you get a bottle of break-in additive to add to your oil. These clearances are needed as a marine engine operates @ 160-170 degrees where autos run a 195-210 degrees. This is why they are a couple hundred dollars more. Will a auto engine work yes, will it last,no
              When in doubt,Trim it out!!!
              Business Owner & Certifed Technician
              Boats I own & use
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              14 x 48 Drifter with 1100SS Merc

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              • #8
                Re: difference between Auto and Marine engines

                Originally posted by Faztbullet View Post
                I dont know where some of these fellows got there info but there is a big difference is a auto vs marine.
                One is painted black, one isn't(usually)

                The mechanicals are the same but camshaft is different so engine will not suck water into cylinders thru manifolds @ idle.
                The cam was mentioned in almost every previous post.

                The internal clearances are different...
                Wrong - GM builds them to the same tollerances as all of thier other engines.

                The is also one reason why Mercruiser specifys 20w40 or straight SAE 30 engine oils.
                They spec heavier oil because it provides better protection under heavy constant load. The car and truck makers have other issues that they decided were more important, like efficiency(every tiny little bit helps)

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                • #9
                  Re: difference between Auto and Marine engines

                  In Truck and even Automotive owner's manuals there is usually a severe duty section that suggests different oils and change intervals. Marine duty would equate to severe duty in Truck/Automotive.

                  A carbed "vintage" Truck/RV engine's cam will be very close to the Marine version so inversion would almost certainly not be a problem in a boat in my opinion.

                  So, a 350 block with the aforementioned changes in core plugs, camming, head gaskets and accessories would be a good "compromise" and last more than a few seasons I bet.
                  1991 HydroSwift 2200 Cuddy Volvo Penta 570/DP
                  1980 Glastron SSV167 90HP Mariner

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                  • #10
                    Re: difference between Auto and Marine engines

                    check out rapido marine out of miami. They are awesome and cheap. They give a warranty and alot of people from this site have used them with good results.
                    www.rapidomarine.com

                    "Reel Justice"
                    Trophy 2059
                    Bravo 1 Drive
                    Mercruiser 5.7 250hp

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                    • #11
                      Re: difference between Auto and Marine engines

                      Michigan motors. Check them out friends bought from them. Reliable and they don't mess around. You get what you pay for from them.

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