Home Forum Ask A Member Top speed with 18hp Evinrude on 14′ aluminum

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  • #51214
    johnny
    Participant

      US Member

      I get 26 MPH on my 14 foot AlumaCraft with my 18 HP 1957 Evinrude. I weigh 185 pounds.

      #51220
      wyo307
      Participant

        Not entirely related but how much more speed are you seeing out of a 25hp or a 30hp of the same erra? I’m thinking the big twins on a 14ft boat vs the 18hp.

        #51224
        olcah
        Participant

          US Member

          My experience is it depends on where you steer the motor from. For a small light boat an 18 HP steered from the rear is near as fast as a 25 hp steered from the front. If you want the most from 18 HP steering from the rear is probably best and lots of fun. A rear steering wheel looks sharp too. I had that setup with a 12 ft boat and new 58 Johnson 18 HP as a kid and often had to turn the throttle back to prevent the boat from flipping over. It got about 26 MPH. If I was real dumb and sat on the transom, it got over 30 MPH.

          My 12 footer using rear tiller steer with 25HP is a bullet and I think would be real dangerous at WOT. (Never got it wide open with rear steering. With a 12 HP Gale I got 22 MPH by GPS). Steering 25 HP or 30 HP from the front it is sporty, lively and controllable but definitely slower(26 or 27 MPH by GPS) than from the rear. If you are steering from the front 25/30 HP is ok. If from the rear, you should investigate a 25 HP before going for one.

          Individual opinions, boats, heartrates and risk tolerance will definitely vary. 😀

          #51232
          wiscoboater
          Participant

            Stephen,
            Shoot me a PM. I have a powerhead for you.

            #52898
            stephenspann27
            Participant

              Update… My motor didn’t actually fail the leak down test, I re tested with the motor locked at TDC and both cylinders passed. I think I’ve tracked the problem down to a bad crank seal at the top. The top spark plug stays perfectly clean, and the bottom plug gets soot on it. I installed a tiny tac and ran the motor for 3.5 hrs today. The max RPM I get is 3,400RPM.
              The reason I think it’s a bad crank seal is because if I spray the top of the block (under the armature plate) with brake clean, the motor will stall. This also would explain the clean top plug (running lean).

              Motor running and being sprayed (you can hear the RPM’s drop, didn’t spray it long enough to kill it)

              https://www.dropbox.com/s/y44llm7isc6g4 … 2.mov?dl=0

              Is this tool the only way to change the seal without taking the case apart?

              #52905
              Mumbles
              Participant

                To confirm the top seal is leaking, you can pour some TCW oil or fuel mix on it and crank the motor over with a socket. This has to be done with the mag plate removed. Removing the spark plugs will make it easier to crank it over to.

                https://www.youtube.com/watch?v=cXt6fV6Z5rc

                You can remove the seal if you don’t have the proper tool or don’t want to split the cases. Punching or drilling some holes in the seal will let you get some screws threaded into it which can then be used to work it out. The bearing is right below the seal so you want to make sure you get any metal chips out before installing the new seal.


                Attachments:

                #52906
                stephenspann27
                Participant

                  That’s a great tip on checking for the leak. I’ll do that tomorrow.

                  #52923
                  dave-bernard
                  Participant

                    US Member

                    I would think if you have a leaky seal then when sprayed it would pickup RPM’s.?

                    #52927
                    stephenspann27
                    Participant
                      quote Dave Bernard:

                      I would think if you have a leaky seal then when sprayed it would pickup RPM’s.?

                      That has been my experience on other engines, but there is always the rule that there should be no change in RPM. I’ll try to confirm it with the oil test sometime this morning.

                      #52934
                      stephenspann27
                      Participant

                        The crank seal is indeed bad. Oil all over everything, including the points, and when I did the oil test, it blew bubbles.

                        Oil test:

                        https://www.youtube.com/watch?v=TpW3erYNrv4

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