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3 litre to 4.3 swap.. Mercruiser

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  • 3 litre to 4.3 swap.. Mercruiser

    Hello all, Just joined on here. I have an 06 Bayliner 197sd deck boat with a 3.0 litre mercruiser engine in it. I've had the boat 8 years now but the motor has never had enough power for me. The boats options were originally the 3 litre or 4.3 new.... Now I'm looking into buying a used boat with a4.3 in it and doing a swap. I've found a 1999 Sea ray with a 4.3 mercruiser for a good price and was wondering if this would be a suitable boat to swap with... I've worked on vehicles quite extensively but don't know I/O s that well to know what would line up and what wouldn't....I figured having a whole boat I'd have everything I need at my disposal... Ultimately I'd like to resell the donor boat with the 3 litre put back in it. Any advice is greatly appreciated.

  • #2
    welcome aboard.

    I would probably just sell the bayliner and use the SeaRay
    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


    • #3
      Not disagreeing, but unlike Scott's thoughts, like you I had a nice boat with a 3.0L that also shipped with a 4.3L.

      I purchased a newer project boat with a 4.3L and a Gen2 in it and decided the way to go was to swap it over. I did have a thread going HERE about the motor mounts and fiberglassing work required. All I can say is I really love the result, more power than I need probably, but that's more fun than less power than I want. The best part of the 4.3L, other than performance, is how quiet it is compared to the 3.0L. To cruise in the thirty something MPH range with the 3.0 things were roaring. I can hold a quiet conversation at 40 MPH with the V6.

      In the end, the swap cost me pretty much just my time as I was able to part out everything I pulled, and the trailer from the donor boat, and paid for the upgrade.

      Note as well, I used EVERYTHING from the donor boat from steering wheel back to prop. I pulled it all, except the throttle handle. That was easier to use the already installed one. The electrical system worked perfectly from one to the other, so that stayed as well, although I did have to redo some to account for an electric fuel pump.
      Last edited by Rick Stephens; August 15th, 2019, 10:45 AM.
      17 Foot '90 Bluewater
      Alpha 1 3.0 Merc - repowered in 2016
      now - 4.3L Vortec - Alpha 1 GenII
      Honda BF100L kicker
      Engine custom - Transom 0D65328 - Drive 0D648864
      If you ain't fishin, then yer working too much.

      Comment


      • #4
        Thanks for the welcome and I appreciate the advice.... I'm looking at the boat Friday and I'm hoping the motor mounts will be the same..Im not sure I want to do this unless I can do a clean swap and resell the other boat. I have my 197 the way I want it so I don't really want to get rid of it
        Last edited by Dennis197SD; August 15th, 2019, 11:34 AM.

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        • #5
          Guess it was kind of a waste of time posting a link to my thread "3.0L to 4.3L mtr mounts and 25 yo transom".

          No, the motor mounts are not the same.

          No, you cannot do a 'clean swap' in a day or two.
          17 Foot '90 Bluewater
          Alpha 1 3.0 Merc - repowered in 2016
          now - 4.3L Vortec - Alpha 1 GenII
          Honda BF100L kicker
          Engine custom - Transom 0D65328 - Drive 0D648864
          If you ain't fishin, then yer working too much.

          Comment


          • #6
            I read the thread when you posted it and it sounded like yours was a nightmare. That's why i was looking for a similar boat and engine setup to avoid doing fiberglass work on motor mounts... If that's not possible then it's gonna be more than i want to get into.

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            • #7
              Is there a reason you couldnt modify your motor mounts with stainless steel adapter brackets instead of doing at all that fiberglass work? And would you recommend that if you had to do it all over again?

              Comment


              • #8
                I had a blast. The only bad part was deciding to redo the transom which realistically was probably not needed.

                Inline engines have a crossmember front mount. All V engines need side mounts. Lots of ways to do a side mount. I didn't mind the fiberglassing of the motor mounts at all. And in the end, I have the perfect fishing barge for my wife and me to go lake hopping for my addiction too kokanee. Every last part of that boat I purpose built and it suits me. And it now will get up over 50 MPH, which it wasn't even in the neighborhood of with the 3 liter. I had a lot of fun that winter building it.... but yeah, I put some hours in.
                17 Foot '90 Bluewater
                Alpha 1 3.0 Merc - repowered in 2016
                now - 4.3L Vortec - Alpha 1 GenII
                Honda BF100L kicker
                Engine custom - Transom 0D65328 - Drive 0D648864
                If you ain't fishin, then yer working too much.

                Comment


                • #9
                  Is there a reason you couldnt modify your motor mounts with stainless steel adapter brackets instead of doing at all that fiberglass work?
                  Ayuh,....... Welcome Aboard,......... The 3.0l has a single motor mount dead center in the front,.....

                  V-motors have a forward motor mount on each side of the motor,.....

                  'n you have to be able to adjust the alignment when it's put together,.....

                  So,.... to answer yer question, I would think the answer is No,.....

                  If yer cobbed together such a beast, I'm thinkin' the engineerin', 'n fabrication would be many times more involved that slappin' in some wood 'n glass like is usually done,.....

                  Don't be scared of glassin',...... it's Easy,......

                  Plenty of help, in the restoration forum,..........

                  Comment


                  • #10
                    My boat has adjustable motor mount brackets on both sides of the 4cyl. Just like any standard v6 or v8 in a car.

                    Comment


                    • #11
                      you will have to post a picture of the only 3.0 to have motor mounts on the side of the motor. all 3.0 motors come from GM with a front mount only.
                      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


                      • #12
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                        Last edited by Dennis197SD; August 16th, 2019, 07:12 AM.

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                        • #13
                          Here are 3 pics of the only one ever....the 2nd pic is the left mount and the 3rd is the right mount (from facing engine)

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                          • #14
                            Wow. That's the first 3 liter I've ever seen with side front mounts. Did not know they made such an animal.

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                            • #15
                              Sign up today
                              My Bayliner had the Ford 2.3 4 cylinder and it too had side mounts. My Mercruiser 120 had the front mount but I was able to make up some side mounts to attach to the side of the block no problem at all. So I didn’t have to try and use the center mount. Made my templates from wood first then sent my designs to a CNC laser cutting shop. Welded them up and they work led perfect. Lots of adjustment. It’s really not too hard to do.
                              1987 Bayliner Capri 1750 (Work In Progress)
                              120 Mercruiser Engine S/N 2458751
                              MC-1 Drive S/N 2463635

                              Bayliner Capri 1750 Bow Rider Rebuild My Way

                              https://forums.iboats.com/forum/boat...s-to-do-it-too

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