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  • Mercury tower of power HP question

    Can anyone tell me what the difference is between the 115, 135, and 150 inline 6's? It looks like the same power head to me. What accounts for the HP difference? Reeds, jetting or is the displacement different?
    Miss Morgan,1969 Sleekcraft "Boats by Nescher" Newport. Power by Mercury 115 L6, tower of power.
    https://forums.iboats.com/showthread.php?t=364284

    Current project,https://forums.iboats.com/forum/boat...project-fuggly

    "Nothing is done so poorly that the government can’t do it worse!"

    “It’s easy being a humorist when you’ve got the whole government working for you.”—Will Rogers

  • #2
    Re: Mercury tower of power HP question

    Most towers after the '60's initiation in white, used a 99 cu in block and yes at the end, just before the advent of the V's they got 150 hp out of 99 cu in. Additionally, I think Merc prop rated all those years which is one reason Merc used to whip the competition hands down who rated hp at the powerhead till the '80's.

    To get 1.5 hp per cu in, they had to do some cute things, but they did: ignition, carbs, intakes, porting, reeds, timing and all that stuff.....yes you are right on.

    I wasn't involved in the process then, but I followed it somewhat beins that I left OMC (as a consumer only) in favor of Merc back in the '70's when I got tired of Merc 125's whipping my Johnson 125's arse all over the place. Haven't looked back and haven't been sorry.

    Best I can do.

    Mark
    If you are new to boating or have a new boat, a knowledgeable friend could show you how to operate your boat and save you a lot of grief, maybe some money, and maybe your life.

    Comment


    • #3
      Re: Mercury tower of power HP question

      Thanks for the info Mark. I had heard they "underrated" them....we had a 115 back in the 80's on a deck boat.....and even on that heavy boat, hang on to your ***, it came out of the hole like a Saturn V rocket! I can't wait to see what the little ski boat I'm restoring will do with one on the stern!
      Miss Morgan,1969 Sleekcraft "Boats by Nescher" Newport. Power by Mercury 115 L6, tower of power.
      https://forums.iboats.com/showthread.php?t=364284

      Current project,https://forums.iboats.com/forum/boat...project-fuggly

      "Nothing is done so poorly that the government can’t do it worse!"

      “It’s easy being a humorist when you’ve got the whole government working for you.”—Will Rogers

      Comment


      • #4
        Re: Mercury tower of power HP question

        Like I said, it could be where they are rated. Also, engines are built to exceed hp ratings so that they can pass production minimum limits. No telling where the top end is.

        Back when I was a kid using tiller small motors on rental boats, hp per hp, if there was a Merc around it was "Boss Hog". Grin.

        Mark
        If you are new to boating or have a new boat, a knowledgeable friend could show you how to operate your boat and save you a lot of grief, maybe some money, and maybe your life.

        Comment


        • #5
          Re: Mercury tower of power HP question

          Arch, The late model ('76-'77) Merc 1500s had power ported pistons and radical timing, which boosted the HP over the 1150 motors. Other than that they were very close in design.

          The earlier 135HP models achieved their power boost in other ways. There is a nice tutorial about the "History of Merc Inlines", which you might like to search up.

          Comment


          • #6
            Re: Mercury tower of power HP question

            Thanks I will look that up.
            Miss Morgan,1969 Sleekcraft "Boats by Nescher" Newport. Power by Mercury 115 L6, tower of power.
            https://forums.iboats.com/showthread.php?t=364284

            Current project,https://forums.iboats.com/forum/boat...project-fuggly

            "Nothing is done so poorly that the government can’t do it worse!"

            “It’s easy being a humorist when you’ve got the whole government working for you.”—Will Rogers

            Comment


            • #7
              Re: Mercury tower of power HP question

              Originally posted by Chris1956 View Post
              Arch, The late model ('76-'77) Merc 1500s had power ported pistons and radical timing, which boosted the HP over the 1150 motors. Other than that they were very close in design.

              The earlier 135HP models achieved their power boost in other ways. There is a nice tutorial about the "History of Merc Inlines", which you might like to search up.
              Is the history of merc inlines on Iboats? I couldn't seem to find it. Thanks!
              Miss Morgan,1969 Sleekcraft "Boats by Nescher" Newport. Power by Mercury 115 L6, tower of power.
              https://forums.iboats.com/showthread.php?t=364284

              Current project,https://forums.iboats.com/forum/boat...project-fuggly

              "Nothing is done so poorly that the government can’t do it worse!"

              “It’s easy being a humorist when you’ve got the whole government working for you.”—Will Rogers

              Comment


              • #8
                Re: Mercury tower of power HP question

                Arch, I was unable to find it as well. I had thought it was posted on this site....

                Comment


                • #9
                  Re: Mercury tower of power HP question

                  Hey Fellers,

                  The history of inlines is on Scream n' Fly.

                  Mark is a bit wrong about the prop rating issue. Merc always underated their inline6s. That said: they did rate them at the crank 'til 1982 when they rated them at the wheel, (prop).

                  He is correct in that they were always underated vs other manufacturers. It was most dramatic in the 1950s butt: corntinued to the last year of the inline6s: 1988. Dunno 'bout the newer stuff.

                  The first production manufactured 100 HP engine, (also the first time Karl painted the VERY purdy ol' girls Black), was a very purdy 89.x cubic inch inline6 that was made from 1962 to 1969, (in 1967 they called it a 950) to differintuate a bit from the 94.x 110 HP engine.

                  The first 99.x cubic inch inline6 was the 1968 125 HP 1250, and after the 1969 model year all of 'em were 99.x cubic inches from the 90HP 900 to the 150 HP 1500. In 1970 they changed the 1250 block, (although still a "silver block") to the 1350 and the 1150, (it is fairly easy to make a 1970-72 1150 a 1350 with reeds n' minor mods to the carbs), THE ONLY TIME in the inline6 lineup you can make a modest change to increase HP, (the rest are best left alone as the factory was obsessed with testing and ya can't beat Karl at his best game).

                  Once Merc went with a bigger cubic inch v-6 they renamed the 1500 a 140, to differentuate from the 150 HP v-6.

                  In 1982 they went to prop ratings and the ol' 1981 140 was a 1982 115 and the ol' 1981 115 was a 1982 90.

                  The prop rated 1982 115 had less flow at the reeds then the ol' 1500 or the 140 so it had somewhat less HP. The difference between an 1982 90 and a 1981 115 is less clear ta me as I have not had those two apart n' I only have one functional brain cell.

                  I hope Ed from Pauslbo, Chris1956, or Laddies or some of the other big guns here on iboats will chime in ta tell us what the difference was between the 1981 115 and the 1982 90 as 25 HP is far more then the 8% to 13% difference from the crankshaft to the propeller.

                  Me overpriced $.02. JR
                  A proud n' rare Independent Cornservative from the Seattle Metro area, who runs the finest old black boat anchors money can buy!

                  Comment


                  • #10
                    Re: Mercury tower of power HP question

                    Thanks Old Mercs for setting that straight. Like I said I was just WAGGING.

                    However, having had one of those 115's of '89 vintage, when did that engine get the Direct Charge enhancement? Mine had it and I just loved it.

                    Thanks,

                    Mark
                    If you are new to boating or have a new boat, a knowledgeable friend could show you how to operate your boat and save you a lot of grief, maybe some money, and maybe your life.

                    Comment


                    • #11
                      Re: Mercury tower of power HP question

                      Originally posted by Texasmark View Post
                      Thanks Old Mercs for setting that straight. Like I said I was just WAGGING.

                      However, having had one of those 115's of '89 vintage, when did that engine get the Direct Charge enhancement? Mine had it and I just loved it.

                      Thanks,

                      Mark
                      Mark,

                      Are ya sure yer Tower was an 1989? Me thinks 1988 was the last year fer the inline6....... sniff sniff, (I could be wrong), only one functional brain cell.

                      The "Direct Charge" first came out in cornsumer inline6s in 1970 with the 1350 n' the 1150 silver blocks.

                      I read somewhere that the 1969 1250 BP has the Direct Charge as well. (Dunno as I have never owned one).

                      Both me 1968 1250s are the earlier 99.x cubic inch models.

                      I own a parts 1971 1150 Silver Block n' a sweet fresh water virgin 1972 1150 Silver Block, both say "Direct Charge" on 'em that the 1250s do not say.

                      Respectfully, JR
                      A proud n' rare Independent Cornservative from the Seattle Metro area, who runs the finest old black boat anchors money can buy!

                      Comment


                      • #12
                        Re: Mercury tower of power HP question

                        Not really to add anything value I'm afraid, but I just had to chime in and say that this year with my first boat a 16foot fletcher gto, the first ever OB engine I experienced on it was a 79' I6 140. Man does it shift. Just hearing you lot talk about them makes me excited haha I love that engine...

                        Comment


                        • #13
                          Re: Mercury tower of power HP question

                          Thanks for all the info, I should have a 86 115 for my restoration project in a week or two....can't wait to get it strapped on to the back of my 16' ski boat and hang on!
                          Miss Morgan,1969 Sleekcraft "Boats by Nescher" Newport. Power by Mercury 115 L6, tower of power.
                          https://forums.iboats.com/showthread.php?t=364284

                          Current project,https://forums.iboats.com/forum/boat...project-fuggly

                          "Nothing is done so poorly that the government can’t do it worse!"

                          “It’s easy being a humorist when you’ve got the whole government working for you.”—Will Rogers

                          Comment


                          • #14
                            Re: Mercury tower of power HP question

                            Originally posted by OldMercsRule View Post
                            Are ya sure yer Tower was an 1989? Me thinks 1988 was the last year fer the inline6....... sniff sniff, (I could be wrong), only one functional brain cell.
                            Last production year was 1988, but ...

                            Originally posted by OldMercsRule View Post
                            The "Direct Charge" first came out in cornsumer inline6s in 1970 with the 1350 n' the 1150 silver blocks.
                            The first DC engine was the 4 cylinder 1969 Merc800

                            Originally posted by OldMercsRule View Post
                            I read somewhere that the 1969 1250 BP has the Direct Charge as well. (Dunno as I have never owned one).
                            The 1969 Merc1250 was a crossflow engine but at the time they also made a Merc1250 SUPER BP THIS one was a DC engine ( Prototype )

                            Originally posted by OldMercsRule View Post
                            I own a parts 1971 1150 Silver Block n' a sweet fresh water virgin 1972 1150 Silver Block, both say "Direct Charge" on 'em that the 1250s do not say.
                            DC engines ( highlights ):
                            • 1969 Merc800, production engine
                            • 1969 Merc1250 SUPER BP ( prototype with a blue printed engine )
                            • 1970 Merc1150/Merc1350
                            • 1972 Merc1400 ( basically the same engine as the 135 but with exhaust tuning and a new bolt pattern between block and leg )
                            • 1973 Merc1500 ( basically the same block as the 140hp but with the addition of "power ports"
                            • 1973 ALL inline 6 engines got the new bolt pattern between leg and block .
                            • 1978 The previous 150 inline 6 engine gets new decals saying 140hp ( NO other differences )
                            • 1978 First year of the Merc1500XS ( 155hp, short shaft, lwp lower unit )
                            • 1979,5 ( mid 79 ) Switched from Dist. to ADI ignition.
                            • 1982 Mercury start measuring the engine hp at the propeller, then 140hp becomes 115hp ( ARE some other minor difference too ), Mercury 115 hp engines ABOVE serial 5829464 are rated at the propeller.
                            • 1984 New power trim unit, integrated as used on the V6 engines .
                            • 1988 Last production year of the inline 6 DC engine .



                            Arne Kjetil
                            My engines :
                            Mercury TII, next project
                            Johnson V4m-10s 90 hp 1964,from the prosess.
                            Mercury L6 ,Rebuilding a Tower

                            Comment


                            • #15
                              Sign up today
                              Re: Mercury tower of power HP question

                              Originally posted by Droll View Post
                              Last production year was 1988, but ...



                              The first DC engine was the 4 cylinder 1969 Merc800



                              The 1969 Merc1250 was a crossflow engine but at the time they also made a Merc1250 SUPER BP THIS one was a DC engine ( Prototype )



                              DC engines ( highlights ):
                              • 1969 Merc800, production engine
                              • 1969 Merc1250 SUPER BP ( prototype with a blue printed engine )
                              • 1970 Merc1150/Merc1350
                              • 1972 Merc1400 ( basically the same engine as the 135 but with exhaust tuning and a new bolt pattern between block and leg )
                              • 1973 Merc1500 ( basically the same block as the 140hp but with the addition of "power ports"
                              • 1973 ALL inline 6 engines got the new bolt pattern between leg and block .
                              • 1978 The previous 150 inline 6 engine gets new decals saying 140hp ( NO other differences )
                              • 1978 First year of the Merc1500XS ( 155hp, short shaft, lwp lower unit )
                              • 1979,5 ( mid 79 ) Switched from Dist. to ADI ignition.
                              • 1982 Mercury start measuring the engine hp at the propeller, then 140hp becomes 115hp ( ARE some other minor difference too ), Mercury 115 hp engines ABOVE serial 5829464 are rated at the propeller.
                              • 1984 New power trim unit, integrated as used on the V6 engines .
                              • 1988 Last production year of the inline 6 DC engine .



                              Arne Kjetil
                              Thanks Arne.

                              What about the 1981 115 and the 1982 90? Were they the same or did they detune the 115 as the did with the 1981 140, (reeds) ta make the 1982 115???

                              25 HP is not lost in the gears!!!!

                              JR
                              A proud n' rare Independent Cornservative from the Seattle Metro area, who runs the finest old black boat anchors money can buy!

                              Comment

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