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Mercruiser MPI V8 with Volvo SX Possible?

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  • Mercruiser MPI V8 with Volvo SX Possible?

    Hi Everyone

    I have recently bought a year 2000 2100 Regal which use to have a Volvo 4.3 engine. The last owner blew the engine and has bought a V8 2006 MPI Mercruiser to replace it with.
    Has a Volvo SX drive

    My question is, has anyone or does anyone know if it is possible to use the V8 Mercruiser with the Volvo drive/transom

  • #2
    Don't see why not, the merc and the volvo are both gm engines
    1999 Powerquest 260 legend
    502 mpi
    B1

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    • #3
      You can, the engines are the same but you will have to remove some or all of the Merc rigging (ie engine coupler, exhaust system if the Merc exhaust elbows won't match up to the VP Y pipe, fuel pump possible, etc). Then there is the issue of the compatibility of the wiring harnesses given that the Merc engine is MPI. While the engines are identical in most cases, there are a lot of differences in the details that can be costly to convert over, esp since you are replacing a 4.3 with a V8, some parts will be different on the Volvo when changing from V6 to the V8. Also, the outdrive gear ratio is for a 4.3, this is going to put the V8 rpms above the level where they should be and this will limit your top speed although low speed acceleration should be very good. Not sure if you can compensate for that with a bigger (diameter and pitch) prop. It would have been easier if you replaced with the same size engine.
      The easiest conversion is with the same size engine and simpler systems (ie carbs instead of MPI). With MPI then you have to have the right fuel pump, sensors and wiring harness. None of this is needed with a simple 4bbl carb.

      Does the previous owner still have the old Volvo rigged 4.3? If so then you would find it much easier to get a reman or new 4.3 and transfer all the Volvo components to it. Less complex, less chance of problems, better resale down the line less to explain to prospective buyers why you have a franken boat.
      Last edited by Lou C; January 12th, 2019, 09:34 AM.
      1988 Four Winns 200 Horizon
      4.3 OMC Cobra

      98 Jeep Grand Cherokee 4.0 Selectrac
      07 Jeep Grand Cherokee Limited 5.7 Quadradrive II

      "While air doesn't freeze....rust never sleeps"

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      • #4
        It may be easier to find a Merc drive setup than to make the engine work with a Volvo drive. You will need a lot of V8 Volvo stuff to make it work. I don't even know if you will be able to make it work as an MPI, maybe with a carb but if you go with a carb you might end up at about the same power as the 4.3l Volvo depending on what it was. What drive was with the MPI? Alpha or Bravo? The computers are different for each.
        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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        • #5
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          I think this might be a good way to proceed- use the Volvo flywheel cover off the V6 (which mounts the engine to transom mounts) and coupler. When I did mine I had to buy SAE bolts vs the metric bolts on the V6 flywheel cover, depends on if your V6 is a 090M casting number

          Your side motor mounts on the V8 will be about 4" farther forward. Your boat probably had a V8 option but check and see if there isn't 4-5" additional space in front of the V6 engine and the side engine mount stringers are long enough to have the engine mounts 4" further forward, if not you have to do some glass work so you can bolt the side engine mounts in. If you don't have 4-5" in front of the V6 you'd have to modify the seat or engine doghouse, which can be done but would be a bunch of work. I'd probably keep a V6 vs modifying the seat or doghouse....

          When i I did this on my 21 ft searay (4.3 to V8 swap) there was plenty of space in front and stringer mounts were set up for both V6 and V8 engines. Just had to drill new holes for lags when I mounted the V8.

          I woudl think the volvo enigine harness has a standard 10 or 14 pin connection to the boat the merc engine should be the same. You may need a 10-14 pin adapter harness depending on what was there in the boat and what the new engine has.

          As mentioned exhaust may require some massaging or fab work, I'd put the engine in and see how it lines up. At worst you can get volvo penta V8 exhaust manifolds and risers to meet up with the Y pipe. Other issues may be throttle linkage and shift cable mounting

          Outdrive ratio i wouldnt worry about, when I did mine kept the V6 drive ratio and steeped up in pitch from a 19"to a 21"

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