Home Forum Ask A Member Shaking at High RPM Running 1955 Evinrude Fleetwin Aquasonic 7.5HP

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  • #183549
    Good-Fishing
    Participant

      So this summer i was running full throttle and had a log strike with my outboard. Ouch… Ive installed a new prop since I the pulled the weeds out from in/behind shaft bearing . Somehow i’m getting water inside the lower unit now. Where should i start, It still runs great at low rpms however when i go to mid to high rpms it bucks crazy like it wants to jump off the boat and no its not an air pocket. Im thinking pinion shock or warped shaft? Yay. Running 1955 Evinrude Fleetwin Aquasonic 7.5HP

      #183561
      bobw
      Participant

        US Member - 1 Year (includes $3 online payment fee)

        Since you are now leaking water into the gearcase, it sounds like a bent prop shaft. Prop shaft seal could also have been compromised by fishing line or excessive weeds.

        Bob

        1937 Champion D2C Deluxe Lite Twin
        1954 Johnson CD-11
        1957 Evinrude Fastwin 18
        1958 Johnson QD-19
        1958 Johnson FD-12
        1959 Johnson QD-20

        “Every 20 minute job is only a broken bolt away from a 3-day project.”
        "Every time you remove a broken or seized bolt an angel gets his wings."

        • This reply was modified 4 years, 7 months ago by bobw.
        #183568
        garry-in-michigan
        Participant

          Lifetime Member

          1954 & ’55 were the first Aquasonics and used springs for isolation. In 1956 they switch to rubber mounts, It sounds like a serious mis-alignment issue. Many of these issues are caused by backing into curbs while trailering with the motor down. Minor hits may be straightened. Major crashes will require replacing parts.











          #183571
          frankr
          Participant

            US Member - 1 Year (includes $3 online payment fee)

            Bucking like it’s going to jump off the transom sounds like a worn out cutch dog to me..

            #183576
            Good-Fishing
            Participant

              In regards to the spring alignment. I tried this first and went ahead and replaced the springs. Still no improvement. It still shifts smooth. I have the lower unit apart now . Just getting to the gear case. No metal shavings in the oil so that’s a good sign.Just not sure if i have to replace the prop seal or something else.

              #183589
              Mumbles
              Participant

                Are you sure the replacement prop isn’t bent to? A bent blade which causes vibration like you describe can be hard or impossible to see visually. A bent propeller shaft should be obvious while turning it with or without the prop on.

                #183591
                Good-Fishing
                Participant

                  Just finished pulling the gearcase. Everything looks alright besides the bearing which was obviously letting the water in so i pulled it. The only trouble the bearing gave me coming off was at the end of the shaft where you place the cotter pin it was sticking. Other than that no problems and it looks straight. The prop i bought NOS in original box because the other one was ruined. Since when you use the old one it just spins and you dont move.

                  #183596
                  Good-Fishing
                  Participant

                    Just pulled The lower unit shock absober. Its stuck and wont move. Tried moving it in vice and with blocks of wood seems like its locked up pretty good probably going to need a new one im thinking that’s the issue.

                    #183597
                    fisherman6
                    Participant

                      US Member - 2 Years

                      Just finished pulling the gearcase. Everything looks alright besides the bearing which was obviously letting the water in so i pulled it. The only trouble the bearing gave me coming off was at the end of the shaft where you place the cotter pin it was sticking. Other than that no problems and it looks straight. The prop i bought NOS in original box because the other one was ruined. Since when you use the old one it just spins and you dont move.

                      When you are referring to the bearing I’m assuming you are referring to the prop shaft bearing head which contains the prop shaft seal. Could you tell if the water was getting past the shaft seal or between the bearing head and the gearcase? There is always a burr on the prop shaft where the drive pin and the cotter pin go through. I always file them off first to prevent gouging the shaft bearing and possibly damaging the shaft seal if it is still serviceable.

                      When you say the old prop was ruined because it just spins and you don’t move, I’m not sure what you mean. Does the propeller spin when the motor is in gear and running and it just will not push the boat? is the propeller just spinning around the prop shaft and not turning in the water? I’m assuming it must be the first scenario since there is no rubber hub or clutch in this prop, only a drive pin that passes thru a hole in the center of the hub extension and the prop shaft. There is a strong possibility that you may have sprung or broken the shock absorber in the top of the gearcase. These things tend to get more brittle as they age. If this is bent / broken / rubbing the bottom of the drive shaft bearing carrier that may be causing some of your vibration also. When these break I squeeze them back together in a vise or a press and weld the seam together. This eliminates the shock absorber effect and necessitates replacing the steel drive pin with a brass shear pin to protect the gears, but it will not destroy the bearing carrier for the drive shaft and it will not break unexpectedly in the middle of the lake and leave you stranded. While a shear pin is not the easiest thing to change on the water, it can be done and you can get back home. If the shock abosrber breaks you will be rowing or getting a tow.
                      -Ben

                      OldJohnnyRude on YouTube

                      #183599
                      Good-Fishing
                      Participant

                        Yes i was referring to the prop shaft bearing and seal. The water was going through the behind the prop into the gearcase you could tell by looking at the bearing,it was lopsided. The prop is a aluminum and bronze prop. It got caught in the weeds and the bronze part was wore off. These specific props dont work without the bronze part.

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