1955 25 HP Johnson Loose Conn Rod Bushings

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This topic contains 9 replies, has 4 voices, and was last updated by Avatar dan-in-tn 2 weeks, 5 days ago.

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  • olcah
    olcah
    US Member - 1 Year
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    #185677

    Messing around with a very worn RD17S. (Even the crankshaft is bad as the internal splines for the driveshaft are worn out). I got compression readings of 94 (top) 89 (bottom). Anyway on opening the crankcase there is definite looseness between the bushings in the rod small ends and the piston pins. The top is loosest but can feel/see play between the bushings and piston pins both top and bottom.

    Would a fix be to replace the bushings? Has anyone ever tried that? Or would there be wear in say the piston that would preclude that? I looked in the parts list and there is no individual number for the bushings?
    Thank you.

    • This topic was modified 3 weeks, 6 days ago by olcah olcah.
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    garry-in-tampa
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    #185687

    The next year they replaced the bronze bushings with needle bearings – and replaced 5,000 powerheads under warrantee when the first bearings used failed. In testing they ran 1000 hours at wide open throttle. It turned out that at an idle the needles rocking back and fourth would ware through the retaining edge of the shell and drop out into the crankcase after around 200 hours.That of course totally destroyed the powerhead. Replacement bearings were a much better quality. Powerhead were sent to the dealers to replace all first production motors. Ralph said that’s what Ole would do. Some owners missed being contacted. Some were pleasantly surprised when the bearing failed five years later and got a brand new powerhead under there one year warrantee.

    If you do remove the wrist pins, be sure the piston is well supported and push on the loose end. (Yes, the pistons are marked “loose” on one side, it’s a tapered bore.) If you push on the tight side, the piston will go out of round,

    olcah
    olcah
    US Member - 1 Year
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    #185698

    Garry,
    Thank you the info above.
    Do you know if one can replace these bushings without changing the pistons and pins? I have not seen a part number for the bushings.

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    garry-in-tampa
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    #185717

    The bushings were cast in, but can be drilled out and reemed to fit the ’56 needle bearings. I was sure I had a service bulletin on replacing those needle bearings, but have not been able to locate it. (next year I have GOT to get organized) The needle bearing part number was 377260 –

    olcah
    olcah
    US Member - 1 Year
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    #185722

    Garry,
    I wondered what was done! Thanks so much.

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    billy-j

    Replies: 91
    Topics: 8
    #185871

    If you want a whole replacement power head I have one. $75.00 plus shipping. Original green paint from a 1955 25 horse 17S. in Ohio. Bill.

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    billy-j

    Replies: 91
    Topics: 8
    #185895

    This is for Garry in Tampa. Do not wish to change direction of this conversation but I have a question regarding one of your replies. Earlier you stated in 1956 they went to needle bearing wrist pin bearings and they were not well designed and failed prematurely in the early 1956 engines. Was there an improved bearing used later in the production year of 1956 ? If so would there have been a 1956 serial number that after would denote an improved bearing design ? Thanks Bill,

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    garry-in-tampa
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    #185905

    Outboards 00001, 2 and 3 were run to death and torn down for analyses. Outboards 00004 through 05000 had the power heads replaced under warrantee. The suppliers specifications changed and the new bearings had the same part number abut were better quality. The only ’56 early serial number Big Twins that you would find with bad wrist pins today would be in an old dealers back room still in the sealed factory box. Any one who didn’t read there mail and ordered the bearings to fix a damaged motor under warrantee was sent a new powerhead.

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    billy-j

    Replies: 91
    Topics: 8
    #185940

    Thanks Garry. Regards Bill,

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    dan-in-tn
    US Member - 2 Years
    Replies: 1000
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    #186094

    Gary, I am now confused. I agree 100% that the ’56 wrist pin bearings were of poor design and caused problems, but I think they were around longer than that? I have found them in ’57 35hp Lark engines. See link:

    http://www.marineengine.com/newparts/part_details.php?pnum=OMC0304322

    That is the original bearing for the wrist pin that it takes two per rod. Still available today. I did not find that the #377260 could be put in the older rod. Some may be heavy enough walled to be teamed, but most are too thin? The 1958 RDE-19 shows the newer style wrist pin bearing you mention. That is the bearing I prefer to use. I just put in the complete conn rod assembly. Just my preference.

    I think Mumbles has made bronze bushings for the original conn rods, but I would rather have a wrist pin bearing, myself.

    Dan in TN

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