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lower unit driveshaft seal

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  • lower unit driveshaft seal

    I have a chrysler 20hp and a 9.9hp. The lower unit driveshaft seal is leaky on both of them. They both have the same seal. I would like to replace the seal without buying the whole seal kit. I need the sierra part number for the seal if they offer it individually. The outside diameter is 1 inch and the driveshaft is 1/2 inch. It is 1/4 inch thick. The water pump housing seal is the same seal if that helps.
    Thanks.

  • #2
    Sierra do not offer only the seal.
    Try Franze Marine or measure the in/out diameter and the thinkness, go to a machineshop and they will find it for you.

    Comment


    • #3
      Need a year or model# for either or both?

      1980 9.9 driveshaft seal: F901307-2
      Or F458307 for the 20 hp. 1980

      2 different part numbers so they might not be the same????

      ​boatsdotnet has parts diagrams figure out what you need?


      Buy American made Cars and Trucks!!!Towing insurance for a boat,a GREAT thing.
      ​Tools to make my life easier: Battery tester, die grinder, temp.gun, compression tester, DVA meter.

      In Scenic , Beautiful San Sebastian by the sea Florida

      88 Bayliner 21CC 2001 Mercury 225 HP EFI

      Comment


      • #4
        Originally posted by jerryjerry05 View Post
        Need a year or model# for either or both?

        1980 9.9 driveshaft seal: F901307-2
        Or F458307 for the 20 hp. 1980

        2 different part numbers so they might not be the same????

        ​boatsdotnet has parts diagrams figure out what you need?

        The 20hp is a 1971. Model 203HB

        The 9.9 is a 1979. Model 92H9F

        I know that the seal is identical in them both

        Comment


        • #5
          The late 20Hp was a downrated 25Hp and it had the 30-35Hp from mid 70.es gearhousing. It is lager with a 2:1 ratio and able to fit a 10 3/8 diameter prop.
          Chryslerman you are right your 20Hp and 9.9Hp has the same driveshaft seal. Early 20Hp had a different LU then the late. They changed it in mid 70.es when they downrated the engines because of prop rating instead of crank rating.

          Do as I said before, try Franz at Franz Marine or go to a machineshop with your measured dimensions and they will help you.

          Comment


          • #6
            9.9 hp 1979 F901307-2 says you need 2 of them?
            They sell some parts here but I don't think they'd have this???
            ​I can't find a parts diagram for the 20 as most places don't list anything past 74???

            E-bay has the seals.
            ​Just put the highlighted part # there and 3 different ones pop up.


            Buy American made Cars and Trucks!!!Towing insurance for a boat,a GREAT thing.
            ​Tools to make my life easier: Battery tester, die grinder, temp.gun, compression tester, DVA meter.

            In Scenic , Beautiful San Sebastian by the sea Florida

            88 Bayliner 21CC 2001 Mercury 225 HP EFI

            Comment


            • #7
              Originally posted by Nordin View Post
              The late 20Hp was a downrated 25Hp and it had the 30-35Hp from mid 70.es gearhousing. It is lager with a 2:1 ratio and able to fit a 10 3/8 diameter prop.
              Chryslerman you are right your 20Hp and 9.9Hp has the same driveshaft seal. Early 20Hp had a different LU then the late. They changed it in mid 70.es when they downrated the engines because of prop rating instead of crank rating.

              Do as I said before, try Franz at Franz Marine or go to a machineshop with your measured dimensions and they will help you.
              Good info to know, thank you very much!
              I also researched jerryjerry05 's part number F901307-2 and from what I can find apparently sierra marine offers the seal individually because when I researched that chrysler part number I came across sierra marine # 18-0593 which should be the same seal?

              Comment


              • #8
                Originally posted by jerryjerry05 View Post
                9.9 hp 1979 F901307-2 says you need 2 of them?
                They sell some parts here but I don't think they'd have this???
                ​I can't find a parts diagram for the 20 as most places don't list anything past 74???

                E-bay has the seals.
                ​Just put the highlighted part # there and 3 different ones pop up.
                The 9.9 only needs one of those seals. The only reason I see for needing two is for the water pump housing which has the exact same seal. I also went ahead and ordered the lower unit seal kit for the 9.9. Apparently the lower unit seal kit for the 20hp says it fits 1972-78 but mine is a 1971.
                Sierra 18-2638 is for the 9.9 but in the picture it looks like it has two of the driveshaft seals and the prop shaft seal. The driveshaft seals. Look identical in the picture. I don't need the pump housing seal so theoretically i would have an extra seal from the seal kit for the 9.9 that I could use for the 20hp? Im just guessing that the second seal is for the water pump housing?

                I'm sorry if this is confusing but I really appreciate the help!

                Comment


                • #9
                  Do you have it apart already?
                  Sometimes there are 2 seals on the shaft???
                  It didn't show the seal as a double in the parts diagram.



                  Buy American made Cars and Trucks!!!Towing insurance for a boat,a GREAT thing.
                  ​Tools to make my life easier: Battery tester, die grinder, temp.gun, compression tester, DVA meter.

                  In Scenic , Beautiful San Sebastian by the sea Florida

                  88 Bayliner 21CC 2001 Mercury 225 HP EFI

                  Comment


                  • #10
                    Originally posted by jerryjerry05 View Post
                    Do you have it apart already?
                    Sometimes there are 2 seals on the shaft???
                    It didn't show the seal as a double in the parts diagram.
                    There is only one seal for the driveshaft on the lower unit. I have not taken it apart yet but I have had it off before to look at it.
                    I drained the 9.9 lower unit a week ago and it was about half water/half oil.
                    The 20hp was pure water.

                    Comment


                    • #11
                      After it's back together??? do a pressure test.

                      ANY grooves on the drive shaft or prop shaft?


                      Buy American made Cars and Trucks!!!Towing insurance for a boat,a GREAT thing.
                      ​Tools to make my life easier: Battery tester, die grinder, temp.gun, compression tester, DVA meter.

                      In Scenic , Beautiful San Sebastian by the sea Florida

                      88 Bayliner 21CC 2001 Mercury 225 HP EFI

                      Comment


                      • #12
                        Originally posted by jerryjerry05 View Post
                        After it's back together??? do a pressure test.

                        ANY grooves on the drive shaft or prop shaft?
                        No grooves on the 20hp. About three weeks ago I discovered that the prop shaft seal was leaking terrible. It was just worn out. I put a new prop shaft seal in it and filled it. I drained it last week to check and it was water again. I pressure tested it and only the drive shaft seal leaks now. The air went out as fast as i put it in. It will hold vacuum though.

                        I Have never completely disassembled the 9.9 lower unit but i figured i should put the whole seal kit in it because I need one outboard that i can run in freezing weather without having to worry about the gearcase freezing and busting. I doubt the shafts have grooves but i will find out when I disassemble it.

                        I will pressure and vacuum test them both after i put the seals in them.

                        Comment


                        • #13
                          IF??? there are grooves???
                          ​I get some fiberglass resin or Marine Tex and fill the groove.
                          After it hardens, I sand it smooth and it usually stops the leaks.
                          The shaft needs to be roughed up for the fiberglass to stick.


                          Buy American made Cars and Trucks!!!Towing insurance for a boat,a GREAT thing.
                          ​Tools to make my life easier: Battery tester, die grinder, temp.gun, compression tester, DVA meter.

                          In Scenic , Beautiful San Sebastian by the sea Florida

                          88 Bayliner 21CC 2001 Mercury 225 HP EFI

                          Comment


                          • #14
                            Sign up today
                            I will keep that in mind if there are grooves. My seal kit should be here friday

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