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Choosing an engine to replace 3.7(Long)

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  • Choosing an engine to replace 3.7(Long)

    Last fall i bought a 1986 Blue Water 19F Executive open bow boat. Has a 3.7L(470) 190HP Alpha 1.
    Runs good, Starts easy but has the broken charge system and i now have the Alt conversion for it.
    So this is more a fun project and nothing that needs done, Just a because i want to project. I Can collect all the parts up over the summer and next winter do the swap.
    Question i have is this.
    According to IBoat spec the boat weighs 2200# and is rated for 230HP max. I can not find a word about it otherwise on the internet.
    Between a 96 or newer 4.3L or a 5.7(any year) What would you do? I have access to either engine for cheap enough and will have either rebuilt to marine spec.
    I know with a newer 4.3L i will need to move to a Alpha 1 Gen 2 setup,exhaust and all the other little stuff. I think it will all work the existing keyhole?
    I believe if i go with a older 350 i would need a new bell housing,flywheel,coupler and upper transmission along with the associated exhaust parts?.
    I never pull skiers, once or twice a summer ill pull a tube.
    Usually i like to cruise around 30/35MPH 3K RPM from my past experience with boats that seems to be close to the sweet spot but sometimes opening them up sure is fun when the wife is not with ya
    Im personally leaning to the 350 but want opinions. Im not bleeding money but this is something i can afford if i start off going in the right direction to start with.
    Thanks guys!


  • #2
    first, you may want to verify the max loading as generally hp limits are on outboards.

    if it was me, i would probably find a 4.3/A1G2 and drop in to replace the 470 you have. however that is also the same amount of work to drop in a 5.7/A1G2

    if you go with any V-engine, you will need to swap out a bunch of parts. easiest is to unbolt what you have, sell it off...... then source a complete motor/drive (complete, as in missing nothing)

    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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    • #3
      Hi thanks for your thought on this.
      I have thought about what you have suggested but i don't think around here i will find the boat i need. Around here you can sell a total POS boat for 2k with what i need and still need to rebuild the engine. so it will probably be easier to piece it together off ebay.
      Part of the reason im leaning to the V8.

      I do have a 1986 350 sitting in my garage for the last 5 years(needs rebuilt). Using that engine i can reuse some of the alpha 1 parts. Will need to buy PS bracket and lines, Bell housing, Exhaust manifolds, Flywheel, Coupler, Y pipe, Upper transmission, Motor mounts and a few other little things i can't think of right now.

      Saturday im buying a good running 97 4.3L from a friend for $100. I would have it rebuilt also. Then i need a complete Alpha 1G2 setup, 4bbl intake new carb, Exhaust manifolds. Will be a significant jump in price.

      Ill have both engines and can go either way right now. So for now im watching CL and see if anything pops up to get me started in one direction or the other.

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      • #4
        Then i need a complete Alpha 1G2 setup,
        Naw,...... The Alpha ya got will run with that motor, even the gear ratio will work,......

        Ya just need the Marine hardware for the motor, 'n a y-pipe for yer Alpha,....

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        • #5
          Hi. Not so long ago, a friend had the same thoughts. He had been through 2 or 3 470 engines and had enough. He planned to drop a 4.3 in. After a bit of research, he decided just to put a new 3.0 in. Simply because this way, he didn’t need to change the gearing (or prop at least) and more crucially, the engine mounts and all the other issues that go with. The 3.0 just went straight in where the 3.7 came out. There surprisingly wasn’t a great deal of performance drop. Ran within 1/2mph and only a little slower to plane.

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          • #6
            Originally posted by Bondo View Post

            Naw,...... The Alpha ya got will run with that motor, even the gear ratio will work,......

            Ya just need the Marine hardware for the motor, 'n a y-pipe for yer Alpha,....
            Really? From reading here i was under the impression you could not make a newer 4.3L bolt up to a old Alpha 1.
            If im wrong and you can i will surly use the 97 4.3L!

            QBhoy. Thanks for mentioning that but im dealing with the two engine choices i have.

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            • #7
              Ayuh,..... A bobtail motor, a 4.3l in yer case, from 'bout '83, to current production can be interchanged, 'n will mount to the drive,.....

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              • #8
                Originally posted by Bondo View Post
                Ayuh,..... A bobtail motor, a 4.3l in yer case, from 'bout '83, to current production can be interchanged, 'n will mount to the drive,.....
                Thanks Bondo!

                Comment


                • #9
                  Originally posted by PatinIdaho View Post
                  Part of the reason im leaning to the V8.

                  I do have a 1986 350 sitting in my garage for the last 5 years(needs rebuilt). Using that engine i can reuse some of the alpha 1 parts. Will need to buy PS bracket and lines, Bell housing, Exhaust manifolds, Flywheel, Coupler, Y pipe, Upper transmission, Motor mounts and a few other little things i can't think of right now.

                  You'll likely need a different ratio drive (1.5:1) and other parts to use the V8 efficiently.

                  Having said that, If I had a choice and time to collect parts, I would go with the 350 V-8 hands down.

                  Usually i like to cruise around 30/35MPH
                  Cruising fuel burn (assuming you're going approx the same speed you indicated), will be approx the same regardless of whats turning the drive shaft. (4cyl, 6cyl, 8cyl) If you like running around at WOT more frequently, fuel burn will follow your "right hand"!

                  But for other things like hole-shot and acceleration, there's NO substitute for cu-in.

                  You'll never be unhappy with MORE power!

                  Cheers,


                  Rick
                  1987 FourWinns 211 Liberator, Originally an OMC 460 King Cobra.
                  Re-powered in 2006 with a 1997 Mercruiser 7.4L Bravo III

                  Comment


                  • #10
                    Yes this has been covered. Thank you

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                    • #11
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                      Gathering a list of the V6 parts i will need to order and there is a couple things i can't figure out.
                      What exhaust Y pipe i will need. Only use Alpha1 or will gen 2 also work?
                      What flywheel. 14in, 168 tooth?
                      What thermostat housing?. Sooo many different styles!
                      Is there a way to use my current 4in heat exchanger on the V6. I believe so but will need to add a expansion tank to the cooling system.
                      I believe i have everything else figured out.

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