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5.0 Mercruiser to Chevy 350 engine swap

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  • 5.0 Mercruiser to Chevy 350 engine swap

    Newbie shadetree mechanic.Bought a winter project.1999 20ft Stingray, 5.0 Mercruiser EFIHas (2) long cracks in the block, (1) per side just above the oil pan.Boat looks like the plug was left in and rainwater filled the boat to just above the location the cracks and froze. (May be irrelevant.)Question:Can I replace the 5.0 Mercruiser block with a 350 engine block? Using truck specs (steel crank, rods, 9.5 pistons, etc.) and marine gaskets.Be blunt. Is it "do-able"? Or am I trying to make chicken salad from chicken manure?All comments and technical tips are welcomed.


  • #2
    Re: 5.0 Mercruiser to Chevy 350 engine swap

    The 305 and 350 are interchangable. Just be sure your long block is built to marine specs. The best part is you will have more ponies to work with for the same price.

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    • #3
      Re: 5.0 Mercruiser to Chevy 350 engine swap

      Good idea,make sure you change the freeze out plugs and gaskets.You may go as far as replacing the heads but the truck application may do.The water pump will have to be replaced as well,unless you fresh water cooled.Charlie

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      • #4
        Re: 5.0 Mercruiser to Chevy 350 engine swap

        Go for It.......The 350 is a Direct Replacement......
        Any Grease is Better,..... Than No Grease at All.......

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        • #5
          Re: 5.0 Mercruiser to Chevy 350 engine swap

          The 350 IS the same block, however...some attention to a few details will make things go much more smoothly, and will be easier on the wallet also. Unless you know for sure that the engine coming out is original, check the code that is cast into the block to determine the year of manufacture. Then buy a block that matches that year range. There were small but important differences over the years & your sheet metal has to match up...among other things.Do you have a 2 bolt or 4 bolt main engine? Oil pans don't interchange. Which side is the dipstick on?Check the starter bolt pattern.Ditto for the flywheel bolt pattern. You get the picture.This is a great upgrade...closest thing you will ever find to free horsepower. I have done three of them & if you are into taking advice I have some for you. Ignore your friends who are great auto mechanics...save yourself a LOT of trouble and money & just buy the da*n marine short block from someone like Jasper.Beware of the cheaper alternatives from Advance, AutoZone etc. Ask to see the rebuild specs on these and you will be amazed at the tolerances that are allowed...mismatched parts...two cylinders bored .040 over & the rest normal and so on...you get what you pay for and these engines can not be expected to last. End of rant.

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          • #6
            Re: 5.0 Mercruiser to Chevy 350 engine swap

            Just a quick thanks on all the info.Please keep it coming.God Bless.

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            • #7
              Re: 5.0 Mercruiser to Chevy 350 engine swap

              Your getting some great advice, none bad that I see!Im a Mechanic so would prefer to build an engine myself so I would know what I am getting, Ive also seen what Relentless mentioned from so called remanufactured auto engines!Id like to experiment with automotive cams for marine use, but its just too time consuming and expensive! I think I would just order a marine cam and be done with it!When I was done I would use a Synthetic gear lube in the lower unit as you are going to be putting more strain on the gears! Also you are going to have to reprop!Go for it!! LubeDude

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              • #8
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                Re: 5.0 Mercruiser to Chevy 350 engine swap

                If I was going to use a high performence camshaft I would look at the comp cams magnum 262 marine camshaft for your smallblock chevy it should really wake your boat up.. Most car cams have to wide a lobe seperation anngle. You need an angle of 109 to 112 degrees. Anymore than this can cause reversion and you will end up with a bunch of bent rods. We all know that water doesn't compress so it's best to keep it out of our cylinders.

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