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dual outboard motors

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  • dual outboard motors

    does anybody have any info about having two outboard motors. I have a 85 16foot larson boat with a 60hp johnson outboard, well i picked up and identical outboard motor and i want to mount both on myboat, the original manual for the boat i have talks very little about the dual motors but it does seem like the boat can have them. so anyway any help would be great thanks

  • #2
    Re: dual outboard motors

    To me, having twins on the back of a 16 foot would look odd, but hey, go for it. I would sell both and upgrade to one big motor if it was me.


    • #3
      Re: dual outboard motors

      Does the manual for your boat tell you the max HP you can put on it ??
      2 X 60hp will be heavier than 1 X 120hp motor and will give lesser performance than a single 120hp.
      However if the manufacturer states in your manual that you can do it then go for it.
      I am assuming that both motors rotate the same way as well ???
      Have you considered the controls yet ??
      sigpicMarada 2100 Executive Series, 5 Litre V8 with Mercruiser Alpha 1 outdrive. 2007 K-Z Spree 260 RBH, all = a whole lot of family fun !!!!


      • #4
        Re: dual outboard motors

        I used to see a small Hydrodyne with twin two-cylinder 50 Johnsons on it. Ran pretty well as I recall. The biggest thing you will need to check will be the side to side engine clearance and the narrow profile of the 60 should work out ok. Also, when you mount the engines the the right and left of the boat centerline, that will affect the mounting position (height)on the transom. Most transoms are made for one engine- in the center. You may have to raise each so that they cut through the water at the right height. Unlikely that the 60 comes in a counter-rotation model, so you will have some big time torque steer to wrestle with unless you go with a hydraulic steering. An interesting project. Good luck.


        • #5
          Re: dual outboard motors

          It's do-able and a lot of fun...especially with the older iron. I run two late 50's OMC Big Twin 35 hp's on a 15-foot early 60's tinny runabout. Had to move the gas tank forward to balance the boat...shorter boats get stern heavy when running twins, batteries, fuel tanks etc. back there. It's fun, but more work. Plan to pull the twins next spring and put an 64 Evinrude V4 60 hp on there and compare performance. Should save me almost 30 pounds on the transom. Might try to find a boat almost the same length as yours with twins and see if you can wrangle a ride/drive...to see if you like it well enough to do it.


          • #6
            Re: dual outboard motors

            I have had a twin installation and like them. That said, unless the boat is so big that it requires more horsepower than is currently available in a single engine, the negatives generally outweigh the positives. Most of the negatives relate to cost and performance. The simple fact of the matter is that twin installations are not as efficient as a single installation of the same horsepower.

            You will carry more weight on the stern and burn more fuel, than you would with a single 120 hp engine. You'll also add the compexity of an extra battery, control unit, tach, fuel tank (unless you have one, large one now), fuel lines, etc. You will also have to change your steering system to accomodate a pair of engines, rather than a single engine.

            Another thing that you will have to do, is to select the right pitch props for the new installation. You need to go to a higher pitch than what you have on the single engine now, but not so high that you can't plane the boat if one engine fails.

            While your boat will go much faster than it does now, it will be slower than if you upgraded to a single, 120 hp engine, with the drag associated with two lower units being the main culprit. Your operating and maintenance costs will also be higher with the twin installation.

            I would also plan on the possibility of having some problems related to torque steer and lean.

            On the positive side, you will enjoy a certain amount of security that you don't get in a single engine. As long as you don't lose power in both engines due to fuel contamination, a log in the water, etc., its rare to have both engines fail at the same time. Increased maneuverability at the dock/trailer is also nice. If you ever do any towing and need to put the boat in a side tow for any reason, you will especially appreciate the ability to control the tow at low speeds, if you have two engines.

            All in all, I would just evaluate the wisdom of the setup in terms of whether or not the boat will perform as it was designed and whether or not you can accept a higher cost associated with the twins.

            Please don't PM me on advice issues - let's keep that in the forums, so that everyone can benefit. Please note that I do not email PDFs, etc. I have a bandwidth limited aircard for internet access. My avatar does not mean I have any offical link to iboats. I just like it!


            • #7
              Re: dual outboard motors

              I way if you want to do it, DO IT.
              I think they look cool. And its something that not everyone has. As far as the worse fuel economy, who cares. Its COOL!!!!
              2011 Triton 190 Escape SE 150 Mercury Pro XS

              I never learned much from winning, but always learn from failure.
              Semper Fi


              • #8
                Sign up today
                Re: dual outboard motors

                Here's a picture of a Mirror Craft Ski n Troll 16 that I modified from the brochure picture. In the brochure it had a single 65 horse, but I thought that was boring. Since the boat is rated for 80 horses I decided to throw dual 40s on the back. After I did it I realized they were 25s, not 40s. The look would be very similar anyway.
                Attached Files
                Cam Milne

                1950 Johnson 5 - TN-26
                1955 Elto 5 (Gale 5 based) - 5D11E
                1956 Eatons Viking 5 (Gale 5 based, incomplete) - 5D12V
                1958 Johnson 7½ - AD-12
                1967 Johnson 9½ - MQ-13
                1971 Evinrude Yachtwin 4 - 4136D
                1976 Johnson 15 - 15R76

                - all from freshwater and built in Peterborough

                "None of us is as smart as all of us"