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Would Like Some Basic Info on the 1989 Mercruiser 3.7 Liter (4-cyl) I/O

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  • Would Like Some Basic Info on the 1989 Mercruiser 3.7 Liter (4-cyl) I/O

    I am hardly familiar with boats, much less the Mercruiser I/O of any kind.

    Looking over a recently purchased Stingray, (17'), I noticed it had a closed cooling system.
    There is a heat exchanger low on the engine on the starboard side.

    I'd like to throw out some basic questions on this I/O/

    1. Did all the 3.7 Ltr.'s have a closed cooling system?
    2. Is this configuration desirable?
    3. Are there any downsides to the 3.7 Ltr 4-cylinder? (That's a lot of liters for a 4-cylinder).
    4. Are there any common problems associated with the 3.7 Ltr. and/or This type stern drive?
    5. What should I look for?
    6. The coolant reservoir looks like it has near 100% anti-freeze in it. How is the heat exchanger winterized?

    Thanks.
    P.S. I may not be able to respond for a day or so, but replies and comments will be read.
    Applicable ones will be replied to.
    Last edited by Barkentine; September 26th, 2017, 12:52 PM. Reason: Corrected year of mfg.

  • #2
    Welcome aboard!

    I take it you have not done a search here on iBoats for the "Mercruiser 3.7 Liter" yet. Plenty of Info and comments, mostly thumbs down and not up for these problematic engines.

    Do some more searches and you will find most of the idiosyncrasies for these, I have included some after the answers to your questions.

    But taking on your questions...:
    1. Yes.
    2. No. (80/20 split on this probably.)
    3. Yes.
    4. Yes, see below
    5. Water in crankcase, normal boat engine telltales (do more searches)
    6. For winterizing, there is a raw water side to the cooling system that needs to be drained, I will not be able to provide details for much of this.



    Here is something I posted a long time ago to a 470-curious member that you may find relevant...

    Maybe you know of these, but here are some typical upgrades and things to watch for with the 470, all of this is from posts here in iBoats..

    External alternator upgrade.
    The 470 uses the same type of charging as an outboard with magnets and stator, with a water cooled voltage regulator. I am probably not getting it quite right, but a very common upgrade is to install an actual pulley driven alternator internally regulated. You need to dig in a bit and scrape the magnets off the back of the balancer, as even though they are no longer used (after this upgrade) they can come loose and sometime even bind up to where the engine won't turn.

    4 inch heat exchanger.
    Yours may already have this, but if it is just the 3 inch then changing it out for the 4 inch is a very good idea and worth the effort. A common demise of the 470 is an overheat, and the head can warp, lots of things go wrong as fallout from the event cascades. With the aluminum head and iron block, and the head floating with no dowels or other locating help this is one thing (bad overheat) that can cause high dollar fix due to hard to find parts.

    Cam bearing seal leaks, another very common epitaph on a 470's tombstone.
    The front cam bearing sealing components almost always eventually fail I guess. There is a speedy-sleeve fix, all I have about this is from reading some very sad posts here. If caught in time while it is just weeping, the speedy sleeve fix can save it. Just depends on how long the engine has been run as water is entering the oil pan the whole time.

    Here is a recent addendum...
    Couple of things with the 470: if you have the alternator conversion, you do not remove the magnets, because the rotor is balanced with them in there, you remove the stator, so if a magnet does come loose it will not jam up. If your weep hole is leaking antifreeze, chances are it is not going into the crankcase because there is a second seal in there to keep it out, as long as the weep hole is not plugged.

    I may be leaving some small items out, and of course your mileage may vary. Another common upgrade is electronic ignition, again searching here can produce some success stories in each of these areas. Some guys here run these very successfully. While you need to be mechanical, when you stay ahead of them you get a lot of power and reliability out of them.



    Last edited by Maclin; September 25th, 2017, 03:06 PM. Reason: spelling
    _

    Comment


    • #3
      The engine is an aluminum block and iron head. Some of the internals are Ford 460 parts. The head gasket blows on overheat because the block is open deck design, meaning the cylinder sleeves are not supported at the top.
      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)


      Comment


      • #4
        Originally posted by achris View Post
        The engine is an aluminum block and iron head. Some of the internals are Ford 460 parts. The head gasket blows on overheat because the block is open deck design, meaning the cylinder sleeves are not supported at the top.
        and as engine designs go, this is what not to do with a motor.

        never have an iron head on an aluminum block. you can have an aluminum head on an iron block
        do not have open deck motors

        the heat exchanger is required on these motors to minimize the temperature fluctuations in an attempt to keep the headgasket from spitting out.
        1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - http://forums.iboats.com/forum/owner...988-rogue-2420

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

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

        Comment


        • #5
          OK guys here do not like them, I am an exception.
          Yes all 470’s have a closed pressurized cooling system with a heat exchanger, just like your car.
          If you are willing to learn how to properly maintain it it is, if you just want to run it and not pay attention to it, it is not.
          Couple of downsides, the head gasket will fail if you overheat it. If the voltage regulator fails it is VERY expensive to replace. The engine water pump cam seals occasionally (every 10 years or so) need to be replaced.
          Do a compression check to determine the health of the head gasket. There is a small weep hole in the lower starboard side of the engine water pump. Make sure it is clear and no antifreeze is leaking out when the engine is running and up to temperature. If leaking your cam seals need replacing. Make sure the electrical system is putting out about 14volts.
          The coolant is a 50/50 auto antifreeze mix.
          To winterize you simply remove the AFT plug from the underside of the heat exchanger, that will drain the raw water side of the exchanger and power steering cooler (if you have one). Takes about 2 min. and you are done.
          I would also suggest that you replace the entire outdrive waterpump and impeller with OEM parts, and then replace the impeller every other year.
          Any other questions, come on back here.
          Welcome to the 470 Club 😉
          Last edited by stonyloam; September 25th, 2017, 10:34 PM.
          Terry
          87, 4WINNS H 190
          470/Alpha I

          Comment


          • #6
            Originally posted by stonyloam View Post
            OK guys here do not like them, I am an exception....
            Nope, you're not. I have no problem with them. For what they are, a 3.7 litre 170 horsepower engine, they do the job very well. But like ALL machines, they like to be maintained and treated well. You can take any GM based engine and neglect it and it will fail just as quickly. '470's have a couple of quirks, that's all. And those quirks are fairly easy to mitigate. The upside is the winterizing. So easy!

            These days the downside is the age. Last one was built in 1989, so genuine parts are getting harder to come by. That said, still plenty of aftermarket stuff available.

            Chris....
            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)


            Comment


            • #7
              Yeah Chris, a few of us like them. I meant to say A LOT OF guys. But what do the two dumbest guys on the site know?
              Terry
              87, 4WINNS H 190
              470/Alpha I

              Comment


              • #8
                Maclin,

                Thank you all for the great replies.

                I could not tell the engine had an aluminum head. The engine paint is shiny and not worn anywhere. The cylinder head is black like the block.
                The engine looks very good. It does not look like its (28) years old. It has not been used in 7-8 years. Turns over fine.
                I agree with the assessment that iron head on iron block is better. Head gaskets don't hold up as long on alum.-on-iron.

                Yes it has the 4" dia. heat exchanger.

                I did do searches on "3.7 Liter Mercruiser" and came up with a lot of extra reading. I'll try it again.

                Thanks for explaining the alternator and the cam bearing seals.

                Comment


                • #9
                  Not denying that some people like them

                  As motor designs go.....its better than the Vazer and the 2.3 Pinto motor that OMG used

                  its a platypus motor, part Ford, Part GM, part outboard

                  it does have a few good points going for it:
                  • neutral balanced flywheel (internally balanced crank)
                  • GM bolt pattern on back end
                  • built out of ford parts bin
                  • HX cooled
                  • 4.36" bore, 3.75" stroke
                  • reasonable compression
                  a few mods help it significantly:
                  • deck girdle (laser cut and tack welded in place)
                  • aluminum head (Edelbrock Ford CJ head with extra hole drilled)
                  • 4" HX.
                  • get the cam reground, nose spray welded and reground, add adjustable rockers
                  • drysump oiling
                  Hot-rodders like it for Model A or T builds. (Its on my bucket list of motor builds).

                  A few things still make me furl an eyebrow:
                  • the cam nose should have been hardened from day one, and the speedy sleeve should have been there from day one
                  • the outboard style charging system was a good idea with a crappy execution. They should have used the flywheel vs the damper as the charging alternator.
                  1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - http://forums.iboats.com/forum/owner...988-rogue-2420

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

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

                  Comment


                  • #10
                    The real question is why would you pick one of these vs a more widely built and supported 4.3/Alpha. Take it from me, owning an OMC, you get tired of hearing that certain parts are NLA, and you get good at figuring out which aftermarket parts are decent, which ones are not, and what Volvo parts can be substituted for OMC (ie center riser exhaust, certain cooling hoses, power steering components, etc). Its easier, and cheaper in the long run to get something that is easy to find parts for and that mechanics are familiar with....
                    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"

                    Comment


                    • #11
                      Originally posted by Lou C View Post
                      The real question is why would you pick one of these ....
                      2 sorts of people buy these engines. Those you know them and know how to look after them, and those you haven't done any research and buy them not knowing what they are buying....

                      Chris.......
                      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)


                      Comment


                      • #12
                        Originally posted by Scott Danforth View Post
                        [*]the outboard style charging system was a good idea with a crappy execution. They should have used the flywheel vs the damper as the charging alternator.[/LIST]
                        What would be the advantage of that?

                        '86 Glastron Conroy X-19, Merc 170
                        '04 Carolina Skiff J14, 25 hp Mercury
                        Richmond/Montross, VA

                        Comment


                        • #13
                          higher output from a larger coil. Add some cooling fins to the back of the flywheel to move air around the coil to help control temps. 50 amps without the cost of a separate alternator. add a bit of logic, some contactors and you could have a built in starter
                          1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - http://forums.iboats.com/forum/owner...988-rogue-2420

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

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

                          Comment


                          • #14
                            The charging sytem, while not the best is adiquate, the biggest problem is that the voltage regulator need to be water cooled, and due to the heating (I think) would eventually fail and need to be replaced. If a replacement cost $50, It would be one thing, but it is more like $500 IF you can find one, so most just convert to a conventional marine alternator. Several good kits out there.
                            Terry
                            87, 4WINNS H 190
                            470/Alpha I

                            Comment


                            • #15
                              Sign up today
                              Originally posted by achris View Post

                              2 sorts of people buy these engines. Those you know them and know how to look after them, and those you haven't done any research and buy them not knowing what they are buying....

                              Chris.......
                              I was a #2, am now a #1
                              Terry
                              87, 4WINNS H 190
                              470/Alpha I

                              Comment

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