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Johnson Sea Horse 7.5, Model AD-11, starts but wont run.

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  • Johnson Sea Horse 7.5, Model AD-11, starts but wont run.

    Well, I just bought my 2nd outboard motor. It's a Johnson 7.5 Seahorse. I believe the year is 1957, model is AD-11. What a classic, great looking motor. I bought it because it will make a great trolling motor on my old Glaspar, and it just looks so classy.
    First I pulled the carbs and cleaned them, replaced fuel lines and bulb, and got fresh gas in the classy looking steel tank.
    It started right up on the muffs, so we went for a launch. It started right up again and backed me out of the dock, we ler her warm up while we rigged up our trolling gear. I put her in gear and started putting forward. When I got into it, she died. Didn't really bog out or act starved for fuel, just shut off fast like a switch was flipped. She started up, ran for 10 seconds and died again and did NOT want to start at all after that.
    So we jigged for a little bit and enjoyed the weather. Pulled her again an hour later and she started right up. Same exact situation though, warmed her up, ran for a minute and died.

    I know VERY litttle about outboards, but with what I know about auto and snowmobile engines, I would guess this to be an ignition issue. I would think that part of the electrical system is overheating possibly and stops giving a spark. We checked for spark and still could see a visible spark, but I'm not sure how to test if it's a "strong" spark. I would think these engines have a coil...could that be what's overheating? I had an issue on my snowmobile where the coil would overheat and machine would die, and ten minutes later it would fire up like nothing was ever wrong.


    Thanks for ANY help!


  • #2
    Re: Johnson Sea Horse 7.5, Model AD-11, starts but wont run.

    ***EDIT*** I just found a website, VintageOutboards.com. Here I can buy a "magneto ignition kit" for 1952-1976 johnsons 3 to 40 HP. It will cost me $90 shippped. I'm somewhat inclined to just purchase this whole kit and replace it all...but money is tight so if I do this I want to be very confident it will fix the problem! Would this be worth the gamble and just replace all these parts? Also, what would the technical difficulty be, I've worked on older jeep and truck engines a lot, and snowmobile engines a little.

    Comment



    • #3
      Re: Johnson Sea Horse 7.5, Model AD-11, starts but wont run.

      Originally posted by tmas suzuki View Post
      Also, what would the technical difficulty be,
      Judge for yourself at the link below by looking at a factory service manual. Good luck with that great old motor!

      Boatinfo - 1922-1964 Johnson Service Manual

      Here's another link with a lot of pictures that I find helpful. Different model but virtually identical to yours.

      http://www.outboard-boat-motor-repai...%20Tune-up.htm
      Last edited by Willyclay; November 21st, 2012, 11:07 PM. Reason: Added link
      Old geezer who never worked a day as a professional in the marine industry but has been fooling with outboard motors for 55+ years!

      Comment



      • #4
        Re: Johnson Sea Horse 7.5, Model AD-11, starts but wont run.

        Take a look at your ignition parts - visible through the window in the top of your flywheel. If the coils LOOK good, 95% chance they are good. Bad ones are usually obviously bad, .ie cracked, burned looking, etc. You can get points and condensers as near as your local NAPA or Evinrude dealer.
        Share A Project Page for 1971 GW Invader Banchie 13
        http://www.shareaproject.com/pages/p...,p,433,00.html
        Share A Project Page for 1976 American 18
        http://www.shareaproject.com/pages/p...,p,404,00.html
        Share A Project Page for 1974 American 15
        http://www.shareaproject.com/pages/p...,p,405,00.html

        Comment



        • #5
          Re: Johnson Sea Horse 7.5, Model AD-11, starts but wont run.

          Has this motor been converted to a fuel pump? Originally, it had a dual line fuel tank that operated on a pressure system. You mentioned replacing the bulb - if it's original, it won't have a bulb..
          Share A Project Page for 1971 GW Invader Banchie 13
          http://www.shareaproject.com/pages/p...,p,433,00.html
          Share A Project Page for 1976 American 18
          http://www.shareaproject.com/pages/p...,p,404,00.html
          Share A Project Page for 1974 American 15
          http://www.shareaproject.com/pages/p...,p,405,00.html

          Comment



          • #6
            Re: Johnson Sea Horse 7.5, Model AD-11, starts but wont run.

            Hi tmas. Great old motor you've got there. For starters, never run vintage motors on muffs. They do not have self priming water pumps. Instead, you'll need to run it in a test tank with water filled up to about 1-2 below the main exhaust port on the back of the motor. These old gems don't have a modern "pee stream" either. Instead the cooling water is mixed with the exhaust gasses and expelled out of the back of the motor. As for the the running and dying issues are concerned, it sounds like you've cleaned the fuel system and the fact that the motor starts and runs at all means the compression is probably ok, which only leaves the spark. You'll need to remove the flywheel to properly inspect and repair the ignition system. Thankfully, it's a cheap, easy DIY job you can do for yourself. You can get a tune up kit with points & condensers right here at iboats, or most NAPA autoparts stores for about $20. You'll also want to run Champion J4C plugs as well. Here are some handy links to familiarize yourself with vintage outboards. Give them a read and let us know if you have any more questions. Good luck. Gobble, gobble!

            Duckworks Magazine

            Vintage Evinrude Johnson Outboard Parts & Diagrams - Catalog ITEM_2831 (parts catalog for an Evuinrude 7.5 hp from the same model year. All part numbers are interchangeable with your motor.)

            Johnson 1957 7 1/2 hp Model AD-11 running - YouTube (I would make the water level 1-2 inches higher than seen in this vid)

            running a 1957 johnson 7 1/2 hp - YouTube (the smoke is normal, don't worry)

            Comment



            • #7
              Re: Johnson Sea Horse 7.5, Model AD-11, starts but wont run.

              You are describing classic symptoms of original coils. Ill bet when you look through the inspection port the coils will be cracked and nasty looking. Dont worry, they had a 100% failure rate and all need to be replaced. OldOutboardJim is the best spot to buy coils, look for him in the webvertize of the amoci.org website. He sells quality coils.

              You should also change the wire while you have the coils off. Get copper core 7mm wire, or any metallic core wire. The dealer is probably the best spot to get it if you're only doing 1 motor. They will sell it by the foot. Get some Champion J6C plugs while you are there as well.
              Chris

              Top Secret Files:

              http://forums.iboats.com/showthread.php?t=299680

              Comment



              • #8
                Re: Johnson Sea Horse 7.5, Model AD-11, starts but wont run.

                Originally posted by HighTrim View Post
                You are describing classic symptoms of original coils. Ill bet when you look through the inspection port the coils will be cracked and nasty looking. Dont worry, they had a 100% failure rate and all need to be replaced. OldOutboardJim is the best spot to buy coils, look for him in the webvertize of the amoci.org website. He sells quality coils.

                You should also change the wire while you have the coils off. Get copper core 7mm wire, or any metallic core wire. The dealer is probably the best spot to get it if you're only doing 1 motor. They will sell it by the foot. Get some Champion J6C plugs while you are there as well.

                The more coils you buy, the cheaper each of them are, too. Four coils cost about the same as a pair does at most suppliers. So, you might keep that in mind, should you decide to add any motors in your collection.
                sigpicVice Admiral Zephyr

                1941 Johnson HD-20 (in restoration)
                1947 Sea King 5hp
                1948 Evinrude Sportsman
                1949 Martin "40"
                1951 Evinrude Fastwin
                1954 Evinrude Fleetwin
                1955 Evinrude Fleetwin
                1955 Johnson JW-11
                1955 Johnson CD-12 (2)
                1955 Johnson QD-16
                1955 Johnson RD-17
                1957 Jhnson CD-14
                1957 Evinrude Big Twin
                1958 Evinrude Fisherman
                1958 Johnson FDE-12
                1959 Johnson RDSL-21B
                1974 Tanaka 1hp (screamin' drink mixer )

                Comment



                • #9
                  Re: Johnson Sea Horse 7.5, Model AD-11, starts but wont run.

                  I buy them 25 at a time from him for a few years now.

                  I was originally ordering batches of 50 and sharing with a couple other members in my area, but have over 100 motors now and almost all are tuned, so as you can imagine I have alot of money in coils!

                  About half that though are 50s OMCS, the rest pre 1950, so they are a whole other ball game. I find Doug Penn one of the best to deal with for the earlier stuff.

                  My "new" outboard is a '76 55hp on my center console fishing boat.
                  Chris

                  Top Secret Files:

                  http://forums.iboats.com/showthread.php?t=299680

                  Comment



                  • #10
                    Re: Johnson Sea Horse 7.5, Model AD-11, starts but wont run.

                    Wow, at that rate, you probably get them about 5 bucks each

                    My last order was for four and I spent like $63. Locally, I spent $62 for two of them. I have a couple more motrs to do, so I'll be ordering more.
                    sigpicVice Admiral Zephyr

                    1941 Johnson HD-20 (in restoration)
                    1947 Sea King 5hp
                    1948 Evinrude Sportsman
                    1949 Martin "40"
                    1951 Evinrude Fastwin
                    1954 Evinrude Fleetwin
                    1955 Evinrude Fleetwin
                    1955 Johnson JW-11
                    1955 Johnson CD-12 (2)
                    1955 Johnson QD-16
                    1955 Johnson RD-17
                    1957 Jhnson CD-14
                    1957 Evinrude Big Twin
                    1958 Evinrude Fisherman
                    1958 Johnson FDE-12
                    1959 Johnson RDSL-21B
                    1974 Tanaka 1hp (screamin' drink mixer )

                    Comment



                    • #11
                      Re: Johnson Sea Horse 7.5, Model AD-11, starts but wont run.

                      Nah once you get over 10 per order they dont go down anymore, he has to make money too!
                      Chris

                      Top Secret Files:

                      http://forums.iboats.com/showthread.php?t=299680

                      Comment



                      • #12
                        Re: Johnson Sea Horse 7.5, Model AD-11, starts but wont run.

                        Oh I know. I was only kidding. His prices are about the best to be found though. I'm definately keeping him in mind.
                        sigpicVice Admiral Zephyr

                        1941 Johnson HD-20 (in restoration)
                        1947 Sea King 5hp
                        1948 Evinrude Sportsman
                        1949 Martin "40"
                        1951 Evinrude Fastwin
                        1954 Evinrude Fleetwin
                        1955 Evinrude Fleetwin
                        1955 Johnson JW-11
                        1955 Johnson CD-12 (2)
                        1955 Johnson QD-16
                        1955 Johnson RD-17
                        1957 Jhnson CD-14
                        1957 Evinrude Big Twin
                        1958 Evinrude Fisherman
                        1958 Johnson FDE-12
                        1959 Johnson RDSL-21B
                        1974 Tanaka 1hp (screamin' drink mixer )

                        Comment



                        • #13
                          Re: Johnson Sea Horse 7.5, Model AD-11, starts but wont run.

                          im spending $60 on two coils, checked all the spots, looked at shipping etc. thats the best price i can get for oem or aftermarket!
                          many men fish for years without ever knowing its not about catching one.

                          Comment



                          • #14
                            Re: Johnson Sea Horse 7.5, Model AD-11, starts but wont run.

                            Email or call Jim

                            The Antique Outboard Motor Club Forums - FS: COILS FOR SALE (western WI)
                            Chris

                            Top Secret Files:

                            http://forums.iboats.com/showthread.php?t=299680

                            Comment



                            • #15
                              Re: Johnson Sea Horse 7.5, Model AD-11, starts but wont run.

                              Originally posted by Chinewalker View Post
                              Has this motor been converted to a fuel pump? Originally, it had a dual line fuel tank that operated on a pressure system. You mentioned replacing the bulb - if it's original, it won't have a bulb..
                              Hmmm interesting. This motor has a dual line tank, but the primer button doesn't work. There is an inline primer bulb...I'm guessing that's been added later. So I guess now I have ANOTHER question....
                              If I have a modern primer bulb on this fuel line...will the pressurized fuel tank work correctly? Or do I need to pull off the inline primer bulb and get a new tank or rebuild the old one?

                              Comment

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