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Can a bent strut be straitened?

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  • Can a bent strut be straitened?

    Hi Guys,

    Bent the prop, shaft and strut on the weekend, want to know if the strut can be straitened. I know the prop can, and the shaft should be able to but cheap enough to replace, but how is the strut straitened?

    The propshaft used to turn easily with my fingers and now takes two hands. I removed the prop, and took the 4 bolts from the coupling to remove shaft assuming it was the bent shaft causing the issue, and the coupling pulled about 40mm (1.5 inches) off center so it seems the strut is also bent.

    Besides the challenges with my engine at the moment we took the boat out for a run on the weekend and hit a submerged object. Depth guage showed over 2 meters (7-8 feet) depth and I had stoped to pick up a skier so at idle. Prop hit and stalled the motor.

    Very little dammage to prop although 1 blade is slightly bent and will be sent for repairs so I did not expect shaft to be dammaged, let alone bend the strut.
    Cheers

    Mark

  • #2
    I'm sure it's not recommended but I did straight'n mine... I'm cheap... Look through my post and there's a thread where I did it. I just used the shaft ever so easily, lil by lil... Like I say, not a recommended method but mine was only slightly bent...

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    • #3
      We just went through this with an old skier over here in NZ, owner also owned an engineering workshop and he took a look at his twisted strut and said "get a new one" problem is that if it is a 100th of an mm out of spec at the strut it will be over 10mm (1000 x) that at the coupler end due to the shaft length.

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      • #4
        Underwater gear is available, just gotta get the right one for your boat. http://www.waterskis.com/200299-p/ma...ft_1_strut.htm

        In terms of straightening I think you'd need to heat/anneal the strut, then ideally you'd know the appropriate alignment, and have a jig had some hardened points that you could use to align the strut.

        As PureInboards mentioned, it has to be pretty straight - but I think the math misses one aspect - the engine is adjustable, therefore you can shift the engine to accommodate for misalignment of the strut.

        In the alignment you center the shaft to account for droop, side/side up down for a neutral position.

        Once you have that position you can shift/slide the engine, so obviously if the strut is out of spec, you end up with an engine that is not inline to the hull, BUT - recall that these are never perfectly inline, all engines are aligned to the strut. The stuffing box floats on a rubber tube to allow for misalignment of the shaft through the stuffing box/shaft log/strut.

        Therefore my suggestion would be 1 - source shaft and prop. Heat and attempt to straigten strut. Install shaft, observe alignment through hull and at engine, if close - realign engine, bolt coupler and verify prop shaft turns freely.

        If alignment is not feasible, then I would replace strut assembly.

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        • #5
          Found a work shop that does regularly straighten these struts abd for the price I am prepared to take it to them. Does anyone have a majic system that I can use to remove the strut easily or is it a case of remove bolts and use big hammer.....?
          Cheers

          Mark

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          • #6
            loosen bolts, leave nuts on. wiggle back and forth till any silicone releases.

            then remove bolts.

            Mine galled real bad when I pulled them, and the bolts were not reusable on assembly. They were also slotted, and I replaced them with Phillips, since you cannot get to both the screw heads and the nuts at the same time, I found it necessary to have someone else run the ratchet while I was under the boat pushing on the screw driver.

            Comment


            • #7
              Originally posted by psychobilly View Post
              I'm sure it's not recommended but I did straight'n mine... I'm cheap... Look through my post and there's a thread where I did it. I just used the shaft ever so easily, lil by lil... Like I say, not a recommended method but mine was only slightly bent...
              I think BriEOD got his straightened by a local shop. I looked into it, but mine was bent so near to the taper that it just wasn't happening. If the bend is farther up the shaft, it can be done.

              /I'm going to reread this post later and snicker.
              Previous: 1993 Prostar 205

              Red 1998 Closed Bow Ski Boat, Ford 351, 310 hp, Acme 4 blade, Perfect Pass SG.

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              To me, this forum is about love of inboard boats. It is about the sharing of information and, on a good day, some humor. It is not about post count, brand of boat, or any other superfluous labels that lend themselves to a false sense of superiority. Please, respect one another, try to pass on accurate information, and keep your eye on the ball.

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              • #8
                Originally posted by Mark rsa2au View Post
                Found a work shop that does regularly straighten these struts abd for the price I am prepared to take it to them. Does anyone have a majic system that I can use to remove the strut easily or is it a case of remove bolts and use big hammer.....?
                Good reading: http://www.mastercraft.com/teamtalk/...ad.php?t=33992
                I love to travel, but hate to arrive. ~~ A. Einstein
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                You donít stop riding because youíre getting old, but you get old when you stop riding.
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                Life should not be a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, in a cloud of smoke, thoroughly used up, totally worn out, and loudly proclaiming, Wow! What a Ride! ~~ Hunter S. Thompson
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                • #9
                  Originally posted by GoneBoatN View Post
                  MMM, have heard of the heat and ratchet method, might try that if a few taps with the mallet does not work.

                  Thanks so far guys!!!
                  Cheers

                  Mark

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                  • #10
                    Strut off easily.. maybe too easily, but it was ok. all 8 bolts out, left it on the shaft and gave it a good wriggle. it budged a little so I tapped it with a rubber hammer and it came away from the hull easy enough with a few more wriggles.

                    Off to workshop tomorrow for prop, shaft, and strut to all get put straight. Then to reverse the process and put it all back together and hope it all lines up ok?
                    Cheers

                    Mark

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                    • #11
                      Update: Strut has been straitened, as well as the prop shaft and the Prop. Workshop tells me the strut and propshaft may have had its last bend and next time it wll need to be replaced... best start saving if the last little bump did that much dammage! (previous Mercruiser leg had about 3 props torn off at speed and no dammage to leg or gear box in 5 years, ended up with Hi5 stainless to stop breaking props).

                      Strut installed, prop shaft insterted and whilst almost in-line L-R, was down by about 12mm. Aligned motor and dropped it but then the sump plug hits the bottom of the hull. Lifted the motor up to give clearance to the hull (+- 1mm) and ensured coupling flange was parallel (0.05mm all round) even though the shaft needed to be lifted about 5mm.

                      Boat ran perfect with out vibration, nice and smooth! I have heard that the 4 mm height difference might affect the strut bushes and the gearbox, but it is smooth. Also figured as I may be replacing the strut soon anyway as they are soo weak, I would not be running this offset for too long.

                      a $350 hole in my pocket, but up and running again! just in time for winter in Australia
                      Cheers

                      Mark

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