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Need advice on replacement 5.7 Merc

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  • Need advice on replacement 5.7 Merc

    So.....I got a 88 Glastron 19CSS Carlson, (full project) and just tore the motor down today.....the heads were all rusted as were the cylinder bores.

    So I need a new motor. This is where the questions come in. Can I buy a used one out of the same vintage chevy truck? I have the exhaust risers and such are all in excellent condition on my motor, so I can swap those over. What about cam, heads, intake, and carb?

    I have no carb....so I definitely need one of those......but as far as the rest of the parts what would I need. I think if I got a 5.7 from a 97 or 98 chevy truck they have the good vortec heads right?

    Thank you for your guidance!
    The Beast: Starcraft Select 170 Mercury Thunderbolt 1150 "If it aint broke, Fix it till it is!" "No good deed goes un-screwed!"

  • #2
    A truck cam will be close enough that it is fine for boating. The heads are the same for boats. Most intakes, especially later, will not work because they are not for carbs. You will need a marine carb. Other things to change are core plugs, water pump and all "externals". Head gaskets are usually recommended to change also.
    83 Sunrunner 16.5 120 merc Alpha 1 drive SOLD 8/1/13

    1996 Crownline 202BR
    5.7l EFI 0f791070
    Bravo I drive

    GMC Yukon tow rig

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    • #3
      Since you need a new motor, find a '96 or later vortec truck motor and pick up a bit more power.

      As Thumpar stated, change the head gaskets and core plugs. Cam only if you want
      Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

      1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - https://forums.iboats.com/forum/owner...988-rogue-2420

      Past Boats
      1970 Wooster Hellion - Merc 9.8
      2002 SeaRay 190BR - 5.0 - A1G2 - "Cheeseheads in Paradise"
      1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

      What’s behind you doesn’t matter.Enzo Ferrari

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      • #4
        Can I buy a used one out of the same vintage chevy truck?
        If you get a pre-vortec motor then all your stuff will bolt back up.

        I think if I got a 5.7 from a 97 or 98 chevy truck they have the good vortec heads right?
        If you get a vortec motor then will need some bracket changes. Any truck motor will work

        The other parts needed have been discussed
        94 Formula 27PC Custom 509MPI MEFI3 , B3 XR
        95 Rinker 232 w/ 7.4L Carb 0F425011 B1 0F486471
        07 Seadoo GTX
        Merc Adults Only VP Adults Only
        G-Dad always said "First Liar doesn't stand a chance"

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        • #5
          Now another question.....What about the new LM series GM truck engines? I know the exhaust manifolds are different.....what else would need replacing? or is that not worth the effort. I can find 6.0L in my area fairly easily.
          The Beast: Starcraft Select 170 Mercury Thunderbolt 1150 "If it aint broke, Fix it till it is!" "No good deed goes un-screwed!"

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          • #6
            The 6.2 was marinized but not the 6.0. I don't know if they used the LM block or the LS block. Either way you would need closed cooling, fuel injection and LOTs of other parts from the marine version that would get very expensive very fast.
            83 Sunrunner 16.5 120 merc Alpha 1 drive SOLD 8/1/13

            1996 Crownline 202BR
            5.7l EFI 0f791070
            Bravo I drive

            GMC Yukon tow rig

            Comment


            • #7
              Both the 6.0 and 6.2 LS motors have been marinized along with the 5.7 and 5.3
              Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

              1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - https://forums.iboats.com/forum/owner...988-rogue-2420

              Past Boats
              1970 Wooster Hellion - Merc 9.8
              2002 SeaRay 190BR - 5.0 - A1G2 - "Cheeseheads in Paradise"
              1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

              What’s behind you doesn’t matter.Enzo Ferrari

              Comment


              • #8
                ok....so I will look for a 96-99 chevy truck with a 5.7.....I dont mind making new brackets, but I dont want to deal with the problems you point out in the LS......

                How much power could be expected from the 96 and newer vortec 5.7?

                Thank you for the help by the way!
                The Beast: Starcraft Select 170 Mercury Thunderbolt 1150 "If it aint broke, Fix it till it is!" "No good deed goes un-screwed!"

                Comment


                • #9
                  Carbureted, around 280. Multi point injected, 300...
                  xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
                  The world takes on a whole new perspective when viewed from 100’ below.
                  1972 Bertram ‘Bahia Mar’ 20
                  2006 Mercruiser 4.3MPI (0W617679) w/Alpha One Gen II (0W829301)
                  (Original - 1972 '165' In-line 6. Previous - 1994 4.3LX)


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                  • #10
                    Originally posted by achris View Post
                    Carbureted, around 280. Multi point injected, 300...
                    and that is prop HP

                    even a bit more if you change the cam and add a carb spacer (or change the cam and re-tune the MPI)
                    Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

                    1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - https://forums.iboats.com/forum/owner...988-rogue-2420

                    Past Boats
                    1970 Wooster Hellion - Merc 9.8
                    2002 SeaRay 190BR - 5.0 - A1G2 - "Cheeseheads in Paradise"
                    1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

                    What’s behind you doesn’t matter.Enzo Ferrari

                    Comment


                    • #11
                      Tell me more about cams and carb spacers..... please?
                      The Beast: Starcraft Select 170 Mercury Thunderbolt 1150 "If it aint broke, Fix it till it is!" "No good deed goes un-screwed!"

                      Comment


                      • #12
                        stock cam is a bit anemic. plenty of cams out there from either Crane, Crower or Comp as an off the shelf cam that will keep you on the good side of reversion (too much cam in a boat is bad). any time you change cams, you need to know the limits of your other hardware. stock vortec heads need to be modified for any lift over .420"

                        for a comp camp, I would run an XM264HR with stamped 1.52:1 roller tipped rockers on a set of vortec heads that have been converted to screw-in studs and have the valve spring pockets cut appropriately http://www.compperformancegroupstore...ry_Code=RFHRXM

                        as for a carb spacer, any time you increase the intake plenum volume, you increase low/mid range torque. a 2" spacer helps the motor from 1500-3500 RPM and gives you a few extra ponies in this range. a phenolic spacer also isolates the carb from the heat of the motor.

                        a good quality high-rise marine manifold would have a similar effect such as the edelbrock RPM performer marine (dual alloy casting)



                        Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

                        1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - https://forums.iboats.com/forum/owner...988-rogue-2420

                        Past Boats
                        1970 Wooster Hellion - Merc 9.8
                        2002 SeaRay 190BR - 5.0 - A1G2 - "Cheeseheads in Paradise"
                        1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

                        What’s behind you doesn’t matter.Enzo Ferrari

                        Comment


                        • #13
                          Originally posted by Scott Danforth View Post
                          as for a carb spacer, any time you increase the intake plenum volume, you increase low/mid range torque. a 2" spacer helps the motor from 1500-3500 RPM and gives you a few extra ponies in this range. a phenolic spacer also isolates the carb from the heat of the motor.

                          a good quality high-rise marine manifold would have a similar effect such as the edelbrock RPM performer marine (dual alloy casting)
                          So would a carb spacer make any difference if a high rise dual manifold is already in place?
                          '84 Grady White Offshore
                          350 Mag w/ Vortec Heads
                          Alpha 1 Drive

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                          • #14
                            What drive do you have? Built motors attached to alpha 1 drives are kind of pointless IMO, because what’s the point in having a high performance engine if you’ve always got to baby it along so you don’t trash your outdrive?
                            1990 Wellcraft Eclipse 196
                            Mercruiser Vortec 4.3 0M322285
                            Alpha gen 1

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                            • #15
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                              Originally posted by FreeBeeTony View Post

                              So would a carb spacer make any difference if a high rise dual manifold is already in place?
                              yes, it will help, however you may run into clearance issues with your hatch. I ran a 1" spacer on my small block with a high-rise
                              Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

                              1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - https://forums.iboats.com/forum/owner...988-rogue-2420

                              Past Boats
                              1970 Wooster Hellion - Merc 9.8
                              2002 SeaRay 190BR - 5.0 - A1G2 - "Cheeseheads in Paradise"
                              1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

                              What’s behind you doesn’t matter.Enzo Ferrari

                              Comment

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