Forums General Discussion Prop Strut Mount


This topic contains 5 replies, has 5 voices, and was last updated by  Dunphyje 7 months, 4 weeks ago.

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  • #224306


    Evening all…
    Mela is on the hard while I do a new bottom job.
    I noticed that the fiberglass on the hull was separating from the propeller shaft strut so I started grinding back the old fiberglass looking for a point where the fiberglass was solidly attached to the strut so I could make a repair..
    What I found was a surprise..
    The strut is mounted in a recessed area about the size of a shoe box that is filled with some sort of waxy fibrous material and then glass over with a fairing compound to the level of the hull.
    The interior of this “shoe box” area is finished with gel coat so it looks like it came out of the original mold that way..
    My questions is.. what type of lite removable water proof filler do you think I could use under the fairing compound to reseal the strut area?..
    Keep in mind that some day it may need to be easily removed to get access to the strut mount for repair or replacement.
    I have attached some cool pictures..
    Thank you for any ideas..

    1. IMG_5270.jpg

    2. IMG_5268.jpg

    3. IMG_5271.jpg

    4. IMG_5280.jpg

    5. IMG_5278.jpg

    6. IMG_5280-1.jpg

  • #224318


    I was hoping someone would have a knowledgeable response for you, John. I’m afraid I don’t either. This is very interesting though, and good to know. All I can think of is to apply some mold release to the portion of the strut that is normally not in view, then thickened epoxy filler or similar to fill up the shoe box. Presumably the filler would adhere to the sides of the shoe box so it would stay put when you are done. I have worked with the mold release material in a past life, and it is, or was, green in color and can be brushed on. Could do a couple of coats to ensure coverage, being careful to keep it off the sides of the shoe box (?). My only thoughts… Please let us know what you do and how it turns out!

    Blue Moon

  • #224320


    Thanks for posting those photos. I’ve wondered what that looks like in there. I’m very interested to hear what you come up with.


  • #224322

    Ken Page

    I don’t think you need any mold release or anything. After I dug out the whole cavity and exposed the strut bolts etc I just scraped all leftover residue from whatever was in there to begin with and all the 5200 that the PO had tried to fill it with. I mixed up some west system epoxy and used #410 filler compound. #410 when mixed with a single pump of epoxy easily quadruples it’s filling capacity. It’s design is for easy sanding and fairing. I “wet out” (just brush a light coating of straight mixed epoxy) the whole area to be filled including the metal, then filled with #410 mixed to the consistency of peanut butter, very thick and no drooping. After it dried I fared with power sander, long board etc to be fair with hull. Final operation a good thick coat of straight mixed epoxy to use as a water barrier. Absolutely guaranteed good to go. I’ve removed many a piece of hardware in various boat yards and with this application the next guy only has to somewhat easily chisel it all out.

    Taking what comes as I get it, using it all as much as I can and trying hard to leave all the shit behind.

  • #224325


    AFAIK, the boat came from the factory without fairing on the strut. The strut with through bolts are exposed in a recess. Some owners fill the space to reduce turbulence and increase speed. I’m not convinced that it helps and I haven’t seen anything that does a good job of filling in the space. I’d suggest cleaning out the old filler and painting it.

  • #224337


    All good ideas..
    Leaving it open would be the easiest but I can just see all the stuff that would grow in there and how hard that would be to keep or get clean when in the water..
    My first idea was to use closed cell foam glued in with fairing compound or 3M 4200 and close over the top of that with more fairing compound.. I want to make sure that it is as water tight as I can make it..
    Not sure what to do yet.. slow thinker I guess..
    I need to find something that will cut thru the waxy substance left behind and I think I should thoroughly clean up, not only the fiberglass area, but also the strut it’s self before I proceed further..
    Also, I am worried about the strut not having a zinc mounted on it… but it does not seem to have very much damage to it as it is after all these years..
    My last boat had a zinc mounted on the strut but a walk around the boat yard only revealed that some sail boats had zincs but most did not?
    I assume the strut it bounded inside as I can not seem to find the strut bolts in the bilge to verify this..
    Your thoughts are very encouraging..
    Thanks for the support..

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