Welcome Guest - Sign Up today
Welcome Guest - Sign Up today

Announcement

Collapse
No announcement yet.

7.5 and 9.8 motor questions

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • 7.5 and 9.8 motor questions

    The two motors im dealing with, 7.5hp blue stripe serial# 4554585 and 9.8hp red stripe serial# 2291925

    ill try to make the long story short, helping a buddy get a motor going for the boat his grandma gave him. The boat came with the 7.5hp motor. The cdi box needs replaced due to brittle and broken wiring, I did manage to solder wires on to what’s left of the wiring and hook it up to the coils to verify spark, good spark so both coils are good, but needs cdi box. Also needs a carb kit, from what I can find he’s going to have somewhere close to $400 for these two parts. So he buys a used 9.8hp

    the 9.8hp runs, we heard it run before purchasing, however it came with two incomplete lower units and a box of parts, he got it cheap enough so I told him I was sure I could figure it out. Yesterday I set to sorting it out, after a while I got to looking at the lower unit on the 7.5, looked identical so I dropped it out and installed in the 9.8, everything fit perfect. Wouldn’t shift to neutral but I think that’s because I didn’t have lower unit in neutral upon assembly. So today I dropped lower unit back out, rotated shift shaft and found neutral, so I should be good there. Checked water pump, vanes all broke off and laying in bottom of pump housing, cleaned it out and realized inside of lower pump housing has some damage that will ruin new impeller, so I remove it and grab the one that came with the 9.8, clean it up and it looks serviceable, go to install it and it won’t fully seat. They look identical, except the area below the main oring that fits down into lower unit housing, is a little longer on the one from the box of parts, than the one from the 7.5. Am I doing something wrong? I measured down to the bearing and it seems like there’s enough room. I looked up the water pump housing replacement kit for the 7.5 and it’s about $100, and it appears the Sierra replacement is NLA. Anyone have any ideas on what I can do to get one of these motors going for him?

  • #2
    Grey housing came from 7.5, yellow housing came from box of parts that came with 9.8. Other pic shows inside of 7.5 pump housing and why I think it will ruin a new impeller. Another side note, the 9.8 came with no lower unit installed, but it had two incomplete lower units and a bunch of parts, the previous owner bought the second lower unit trying to diagnose why he couldn’t ever get the motor into neutral, which I’m now thinking was his installation error
    Last edited by 870 Expressmag; February 10th, 2019, 07:03 PM.

    Comment


    • #3
      These are not in the same family. Blue stripe and brown stripe motors are the same (80-85)

      The red stripe motor is a 68-72

      Major changes between them, very little crosses
      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

      Comment


      • #4
        Last year for the red stripes was 71*, in 72 Merc switched to blue


        *execpt for 3 motors in an XS line in the late 70s which used red decals

        Comment


        • #5
          Well as far as I can tell when I installed the lower unit from one motor to the other everything will work, so do I just need to get the water pump pieces for the 7.5 since that’s the LU I’m working with?

          Comment


          • #6
            Sierra 18-3446 looks to be the pump kit for the 7.5hp LU, am i correct?

            Comment


            • #7
              there are two diameters of lower unit shafts for the 7.5 and 9.8 you have to measure what you have, and get the correct one.
              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

              Comment


              • #8
                All the shafts I have are the .456 and the old impeller measures the same, is the 18-3446 correct?

                Comment


                • #9
                  yes, that is the kit that should be .456 vs the .439
                  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

                  Comment


                  • #10
                    you do know that the blue stripe motor has a stainless shaft and your red stripe has only a steel shaft. one of the many changes that came along
                    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

                    Comment


                    • #11
                      will the stainless vs the steel shaft be a problem? since i'll be putting the blue strip LU into the red stripe motor the stainless shaft will be in the motor we are assembling

                      Comment


                      • #12
                        shouldnt be a problem, just pointing it out.
                        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

                        Comment


                        • #13
                          So I got the water pump kit, everything assembled good and as planned, put everything together, and for the life of me cannot get the lower unit into the motor, I know I’m getting hung up on the shift shaft. I’ve rotated shift shaft on LU and verified I’m in neutral, places powerhead in neutral, doesn’t matter which way we hold it, sideways upside down leaning this way and that, no go. Even slightly moving powerhead shift lever doesn’t allow them to slip together, only way we can get it together is when the upper shift shaft moves far enough sideways and they don’t mesh, but then we can shift the lower unit. I’ve read tips and tricks, watched YouTube, this thing just don’t wanna go

                          Comment


                          • #14
                            ok so ive figured out the problem, now to figure out how to fix it. i took a spare lower shift shaft, placed it into the 7.5 which the LU was removed from, it fit, i then took the same shaft, inserted it into the 9.8, it also fit, so in theory the shift shaft in the LU from the 7.5 will fit into the 9.8. now i took that same spare shaft, turned 9.8 upside down and placed it in neutral, inserted the spare shift shaft and then removed, noting which way the flat portion of the shaft faced, then took the lower unit im trying to install, verified it in neutral, and held above the motor as if to insert lower unit, and the flat from the shift shaft in the LU faces a different direction, about a quarter turn off. so this is why i cant get the lower unit in correctly. is there a way to change this direction so the two will mate together?

                            Comment


                            • #15
                              Sign up today
                              im thinking i can seperate the upper shift shaft from the upper shift shaft gear sector and turn it the quarter turn i need?? no i need to pull the engine block to get this shaft up and out??

                              Comment

                              Working...
                              X