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Honda 50 Lower unit Cracked

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  • Honda 50 Lower unit Cracked

    My Honda 50(1999) has a piece(clamshell shaped) of the gearcase missing fron the back edge of the case and runs forward about 3.5"s. It is and 90 degree arc at the back edge and runs out just forward of the bearing retainer rear section. The retainer nut is cracked just behind the prop. The moter runs fine at low speeds, but cavites at 5000. the propshaft part stack is tight axially and doesn't wobble.
    Any thoughts on why this happened and is it a common Honda problem?

  • #2
    Re: Honda 50 Lower unit Cracked

    pretty common on motors of that age...corrosion builds up between the bearing carrier retainer and the housing and forces the housing out further and further until it pops out a chunk...seen lots of 50's do it..seen it on Mercs,Mercruiser,rare on Yammies but happens


    • #3
      Re: Honda 50 Lower unit Cracked

      Don't know, but my in-laws 40 HP merc had a similar hunk missing from the cav plate. The motor was used only for a couple of weeks on a lake. There wasn't any indication of trauma...just a clean break.

      We couldn't figure it out, but we started stretching our ideas to some sort of "harmonic vibration" that found a weak spot in the alloy...you know, kinda like the wine glass shattering with sound. Probably not a chance as to the reason, but it made as much sense as anything else!

      "New" '57 Lark Chapter One...the Find:

      "New" '57 Lark Chapter Two...the Initial Breakdown:

      "New" '57 Lark Chapter Three...the Gearcase:

      "New" '57 Lark Chapter Four...the NOS Powerhead:

      "New" '57 Lark Chapter Five...Repainting:


      • #4
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        Re: Honda 50 Lower unit Cracked

        Your description is a little vague but if I'm reading it properly ,that sounds like freeze damage.Is that concievable?