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mercruiser 170. 1985 info info on block-gctid391538

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    mercruiser 170. 1985 info info on block-gctid391538

    I have to rebuild the engine on a project boat, I have 1 dead cylinder by dead I mean almost 0 compression, just a little more than 10 percent difference lol. is it a 3.0 or 3.7 block, I am pulling it apart this week. This is going to be my first engine rebuild, I have done several swaps from short blocks on 4.3 and 5.7l but this is my 1st 4 cyl at all so I figure I will tear it down and hammer it out myself. I cant see paying the same for a 8 cyl block and a 4 cyl block.

    #2
    The 470 (170 hp) was the first motor that Merc actually built themselves. It's life began as a GM V8 that was literally cut in half. That's the reason that the cylinders are as large as they are, and they were able to get 170 hp out of them (185 with a cam and 4 bbl carb.)

    I tore mine down many years back and had a machine shop do all of the boring, truing, etc. Some folks didn't have much luck with the 470, but I doubt that I'll ever have another engine that serves me as well.

    I've got the manual for it, so if you'll let me know what spec's you need, I'll get them to you. Bob.
    Bob Hawes.
    Kelowna, B.C.
    1998 Trophy 2052 WA
    4.3 Vortec, A1 G2

    Comment


      #3
      The Merc 470 may have the GM rear engine flange pattern......., but the roots come from the 385 series Ford.

      The cylinder head is actually a 385 series 460 Ford cylinder head.

      The 460 bore/stroke is 4.360" x 3.850".

      Since one half of 7.4L is 3.7L , and I can only assume that the Merc 470 followed suit.

      These did not live a long life in the Mercruiser line up.

      I'd suggest that before you do this, you look carefully at some of the components.

      Charging system... very problematic.

      Front cover between the camshaft and engine circulating pump... the camshaft drives the circ pump.... these share a common sealing point.

      Top of the bores.... this is an aluminum block engine.

      Many will suggest that you find an alternate engine.

      .
      Rick E. Gresham, Oregon
      2850 Bounty Sedan Flybridge model
      Twin 280 HP 5.7's w/ Closed Cooling
      Volvo Penta DuoProp Drives
      Kohler 4 CZ Gen Set

      Comment


        #4
        thanks for the input guys, rick I thought I remembered something about the 170 and that was it, I was warned years ago not to buy one, well I technically didnt buy this I traded an atv that we dont use any more for it, it was only worth 750 or so so I am still good. what engine is a similar Hp that would plug right in so I dont have to change the drive

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          #5
          Hi Rick. I've heard numerous people say on this forum that they'd never have another 470. I'm wondering if there were different motors north of the border? They were a very common and reliable motor in B.C. I'd spoken to numerous owners and have ran 3 different boats with them (some with twins). They all ran flawlessly and my last one (which had 1 rebuilt in close to 25 years) was still running well when I sold the boat 3 years ago. The rebuild was the result of an unfortunate incident that was no fault of the motor. They came with a totally closed cooling system, and required very little maintenance. Go figure??
          Bob Hawes.
          Kelowna, B.C.
          1998 Trophy 2052 WA
          4.3 Vortec, A1 G2

          Comment


            #6
            I have never been a fan of the 170 / 3.7l or whatever other name written on the engine. The head design is terrible. The head and the block are made of 2 different metals. The charging system forgetaboutit. The exhaust pipe is another problem.

            But the weight to power this little power plant is unequaled until just recently.

            Shoot us a picture. Of the engine.
            Be good, be happy, for tomorrow is promised to no man !

            1994 2452, 5.0l, Alpha gen. 2 drive. Sold ! Sold ! Sold !

            '86 / 19' Citation cuddy, Merc. 3.0L / 140 hp 86' , stringer drive. Sold ! Sold ! Sold !

            Manalapan N.J

            Comment


              #7
              Chief is correct! These were strong little engines with lots of torque!

              bbruno wrote:
              ............. what engine is a similar Hp that would plug right in so I dont have to change the drive
              The over-all drive ratio was unique to the 170 (470), and I don't recall what it was.... but it is a special ratio.

              The universal drive shaft may also be either long or short.... I don't recall!

              As for another engine, I believe that you could use any engine that Merc previously used. However, you'd want to make certain the the inner transom plate and the replacement engine flywheel cover were compatable.

              You'll want to speak with a well seasoned Merc guy for this info.

              If you choose to run one, I'd take the time to remove the front cover, examine the camshaft seal surface, replace this seal, and button it back up.

              I'd then remove the OEM charging system, and replace it with Delco 10si kit.

              bhawes wrote:
              Hi Rick. I've heard numerous people say on this forum that they'd never have another 470. I'm wondering if there were different motors north of the border? They were a very common and reliable motor in B.C. I'd spoken to numerous owners and have ran 3 different boats with them (some with twins). They all ran flawlessly and my last one (which had 1 rebuilt in close to 25 years) was still running well when I sold the boat 3 years ago. The rebuild was the result of an unfortunate incident that was no fault of the motor. They came with a totally closed cooling system, and required very little maintenance. Go figure??
              Bob, I don't disagree.... they were strong engines.

              The weak links were the Merc charging system (easily fix-able) and the engine circulating pump impeller arrangement. They drove the impeller from the camshaft. There is a cover and seal arrangement that separates the engine oil side directly from the Ethylene Glycol side.

              These are two areas that we'd never want to see breach separation. Bad Ju Ju!

              The cylinder head was a 385 series Ford (460). I don't think that there were cylinder heads issues.

              There may have been issues with the aluminum block to cast iron head..... but all of these were Closed System Cooled.

              With a twin engine boat, often the center-to-center dimension prevented repowering with V-8's.

              .
              Rick E. Gresham, Oregon
              2850 Bounty Sedan Flybridge model
              Twin 280 HP 5.7's w/ Closed Cooling
              Volvo Penta DuoProp Drives
              Kohler 4 CZ Gen Set

              Comment


                #8
                I know it could be several things, rings, valves, head gasket, cracked block, but one has to be most common to give me hope its something simple, I still think I want to fix it, the engine runs but vibrates like crazy, I cant hear a tapping or knocking sound at all

                Comment


                  #9
                  I think almost any engine can be rebuilt. But just because you can do something doesn't mean you should.
                  Be good, be happy, for tomorrow is promised to no man !

                  1994 2452, 5.0l, Alpha gen. 2 drive. Sold ! Sold ! Sold !

                  '86 / 19' Citation cuddy, Merc. 3.0L / 140 hp 86' , stringer drive. Sold ! Sold ! Sold !

                  Manalapan N.J

                  Comment

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