Moving a reducing gear to a direct drive A4

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  • Grappler
    Frequent Contributor
    • Apr 2015
    • 7

    Moving a reducing gear to a direct drive A4

    The A4 in my Columbia 36 has been getting very hard to start, and running poorly, with low compression (68-80 psi). It has the reduction gear housing.

    A friend who rebuilds marine diesels has an A4 that he acquired recently that appears to be a newer model than mine. It starts readily, runs, and has 90 psi compression on all cylinders.

    I thought it could be drop-in compatible replacement for my A4 till I discovered that it doesn't have the reduction gear housing. So it's about 5" shorter than my A4. I thought this might be ok if I just got a longer prop shaft, but then realized I'd also need a different prop. And now I see from the A4 manual and from one of the posts on the forum that the height of the output shaft is 1.042" higher on the direct drive A4, so if I use it, I'll have to lower the engine by that amount to line up with my prop shaft. This would be very difficult. I'd have to remove material from the existing fiberglass engine supports.

    So now I'm thinking I might be better off moving the reduction gear from my old A4 to the newer A4.

    Can anyone point me to some hints/advice/instructions for doing this? I haven't found much in this forum, but see that some people transplant the reduction gear with the reversing gear.

    Thanks.
    sigpic
    Craig Wiklund
    Allegro (Columbia 36), Red Cliff, WI
    Nansen (Chrysler 26), Bloomington, MN
  • tworail
    Frequent Contributor
    • Feb 2019
    • 6

    #2
    I don't have any experience in moving the reduction gear or even know much about it, but it sounds like a lot of work that I would be trying VERY hard to avoid at all costs.

    Is your current engine up to date on all maintenance, upgrades, etc? I had low compression in mine as well - actually quite similar numbers to yours - in a dry test, and I need to do a wet test as well.

    But that alone isn't a terminal condition or reason to ditch the engine, since the A4 is known for having lower compression numbers, and it depends alot on the tests you are performing as well.

    Carb cleaned, serviced and adjusted as per the Moyer manual? Fuel supply/filters inspected/changed, is there any possibility of water in the fuel system? What do your plugs look like, wet, dry, sooty, fouled? Hints from other parts of the engine subsystems that might indicate there is trouble?

    I would want to rule out ALL the possibilities with the current engine before looking at an engine swap. I'm sure others will chime in and offer assistance on the issues you may be facing.

    Spring startup is always a tricky time (assuming you don't use it all year) it took me many hours of maintenance work and troubleshooting to get everything sorted out and up to snuff, and it didn't start out that way - once I got the engine running it quit a short time later, even after opening the raw water pump (turned out to be rich condition on carb and improper idle adjustment) but sent me down a few rabbit holes trying to figure it out.

    Thought it was a clogged fuel vent line, nope, and that takes a long time to manifest (apparently 15-20 min), thought it was a coil problem, thought the carb had water in it, etc etc. Turned out to not be anything complicated and I was happy to run the engine in gear at the dock for 30 minutes to give some level of comfort that it was ready to leave the dock and find the next gremlin during a sea trial when we can really put it to the test.

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    • msmith10
      Afourian MVP
      • Jun 2006
      • 475

      #3
      That's a lot of boat to be pushing with a direct drive A4, which is why the reducing gear was there. I don't think you'll be happy without it. As tworail says, I'd get more information on the current engine before swapping out, and I'd assume you will need the reducing gear in any event.
      Last edited by msmith10; 05-21-2023, 07:11 AM.
      Mark Smith
      1977 c&c30 Mk1 hailing from Port Clinton, Ohio

      Comment

      • Dave Neptune
        Afourian MVP, Professor Emeritus
        • Jan 2007
        • 5116

        #4
        I had a 35 footer with a direct drive and would of loved to have had the reduction unit. The extra power it gives you really helps.

        Although I have no experience exchanging one it can't be that big of a deal as you would have all of the parts. There are many on the forum who have done that task and they will probably chime in. Changing the mounts and starting from scratch on alignment would be a lot more work by far. Why change it when you have the superior unit in hand that will bolt up to the new motor and fit?

        My 2 cents.

        Dave Neptune

        Comment

        • ndutton
          Afourian MVP
          • May 2009
          • 9780

          #5
          The reversing gear is different for a reduction gear so it will have to be swapped too. The smart move is to keep them as a single unit when swapping over. It's not a huge job with experience. I helped with such a swap 50 years ago and as I recall it took less than an hour.
          Neil
          1977 Catalina 30
          San Pedro, California
          prior boats 1987 Westsail 32, 1970 Catalina 22
          Had my hands in a few others

          Comment

          • Grappler
            Frequent Contributor
            • Apr 2015
            • 7

            #6
            Thanks guys!

            I should have mentioned that we already have the old engine out sitting on the ground.

            The old engine had spark, and the plug wires were not reversed. I believe the carburetor is in good shape, though it was about two or three years since I last removed and cleaned it. But even with starting fluid sprayed into the intake, I had a hard time starting it. It would crank for a very long time before gradually starting to fire and accelerate, and be capable of running on its own. The compression numbers were lower last year than what they were the previous year and the starting and running was getting worse. It’s got electronic ignition. I verified the valve clearances were to spec last fall. This spring I added, Sea Foam to all of the cylinders and cranked a few turns and left it sit for a few days to see if it might free up any potentially sticky rings or valves. But that did not have any effect on the compression numbers.

            I always took care when I was winterizing it, changing the crank case oil before laying it up, fogging the cylinders, putting antifreeze in the block. Some years I also put marvel mystery oil in each of the cylinders in the fall, though I did not do this every year.

            There was no water in the fuel last year, but I have had water in the fuel a couple of times previously. The water would cause it to sputter and die but when I got rid of the water, it didn’t continue to have a problem with starting and running.

            I have the Moyer Atomic 4 Service Manual 1st Edition. It doesn’t really have any information about the reduction gear. And not much information about removing or replacing the reversing gear.

            I have the Universal/Westerbecke A4 Operation and Maintenance Manual. It does not have any information about the reduction gear.

            I have the Universal/Westerbecke A4 Parts List manual.
            sigpic
            Craig Wiklund
            Allegro (Columbia 36), Red Cliff, WI
            Nansen (Chrysler 26), Bloomington, MN

            Comment

            • msmith10
              Afourian MVP
              • Jun 2006
              • 475

              #7
              Originally posted by ndutton View Post
              The reversing gear is different for a reduction gear so it will have to be swapped too. The smart move is to keep them as a single unit when swapping over. It's not a huge job with experience. I helped with such a swap 50 years ago and as I recall it took less than an hour.
              Neil- If it took you an hour, it would take me 8.
              Mark Smith
              1977 c&c30 Mk1 hailing from Port Clinton, Ohio

              Comment

              • msmith10
                Afourian MVP
                • Jun 2006
                • 475

                #8
                If you follow the link below you can download an original manual for the Paragon reversing gear with reduction gear. I just browsed it quickly so it may not be helpful, but look it over.

                Mark Smith
                1977 c&c30 Mk1 hailing from Port Clinton, Ohio

                Comment

                • ndutton
                  Afourian MVP
                  • May 2009
                  • 9780

                  #9
                  Originally posted by msmith10 View Post
                  Neil- If it took you an hour, it would take me 8.
                  You give me too much credit. I was the helper learning alongside someone with experience.
                  Neil
                  1977 Catalina 30
                  San Pedro, California
                  prior boats 1987 Westsail 32, 1970 Catalina 22
                  Had my hands in a few others

                  Comment

                  • Grappler
                    Frequent Contributor
                    • Apr 2015
                    • 7

                    #10
                    Thanks Mark for the Paragon manual!

                    I was using it today to try to move the Reduction Gear and the Gear Case Assembly from my old A4 to my newer A4.

                    After seeing the photo of these two assemblies, still joined together, for sale in the Moyer Marine online catalog, I was hoping I could get them out without removing the reverse gear housing (67). But my actual parts don't quite match the parts shown in the manual. In order to get the yoke (79) out of the way, to be able to slide the gear case assembly (the big cylindrical assembly that resides inside the reverse band assembly, which is inside the reverse gear housing) out the back of the engine, the cross shaft (78, the shaft that goes through the back of the reverse gear housing, to which the external shift lever attaches) needs to come out. But there are some woodruff keys on the underside of the cross shaft that don't seem to be accessible. The Paragon manual shows the cross shaft as being two separate pieces, but in both of my motors the cross shaft is one piece.

                    I hesitate to remove the reverse gear housing because it seems like more opportunity for things to go wrong and leaks to be created when I put them back together.

                    Can anyone summarize the steps needed to remove the reduction gear and gear case assembly out of my old A4?

                    Thanks,

                    Craig
                    sigpic
                    Craig Wiklund
                    Allegro (Columbia 36), Red Cliff, WI
                    Nansen (Chrysler 26), Bloomington, MN

                    Comment

                    • Al Schober
                      Afourian MVP
                      • Jul 2009
                      • 2034

                      #11
                      Your old A4 has the reduction gear. The replacement A4 does not. No worry.
                      I've done this change - not hard.
                      The reversing gear from the old A4 has splines on the aft end of the reversing gear. You need to take the internals of the splined reversing gear (the stuff that rotates) and transplant it into your new engine.
                      Do not swap the reversing gear housings. They are mated to the block and oil pan with dowel pins.
                      Also recommend you install the stainless shifter shaft into the new engine. Get rid of that corrosion issue. Hopefully they'll be in stock soon!
                      Save the old reversing gear. You may need parts from it in the future, in particular the shifter cone.

                      Comment

                      • Grappler
                        Frequent Contributor
                        • Apr 2015
                        • 7

                        #12
                        Thanks Al.

                        I did need to take the reverse gear housing off the new engine in order to remove the reverse gear case (the rotating cylinder/guts of the reverse gear/tailshaft assembly). Even if I could have gotten the yoke out-of-the-way, the reverse gear case was larger in diameter, and the opening through the two halves of the housing.

                        Now I am trying to do the same thing on the old engine. After removing the reduction gear assembly, I am trying to remove the driving gear from the drive shaft. In order to do that I need to get the nut off. But I am not able to stop the shaft from turning while applying torque to the nut. I think I can stop it from turning if I wedge a screwdriver in between the reversing band and a clutch disc of the reversing gear. But I am hesitant to do this for fear of damaging it, and wonder if there is a better way.
                        sigpic
                        Craig Wiklund
                        Allegro (Columbia 36), Red Cliff, WI
                        Nansen (Chrysler 26), Bloomington, MN

                        Comment

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