1956 javelin 30hp

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  • clemg

    US Member - 1 Year (includes $3 online payment fee)
    Replies: 73
    Topics: 20
    #11223

    I will try to explain this as best I can.
    Started to tear down the power head. I took the head off and intake. I hand cranked the motor over and noticed a little play whe top piston is at top dead center. It sounds like a poping sound. I put my fingers on the top piston and hand turned again and I can feel some play on the top piston. Is this normal or do I have issues!
    Any advise would be great!!!
    Clemg


    adam1961

    Canada Member - 2 Years
    Replies: 366
    Topics: 88
    #82938

    These motors are often a little loose as you described. 1956 was the first year for a needle bearing at the wrist pin end of the rod. They were and improvement over the bushing from 1955 and earlier, but still too small. Turn the motor so that the rod is pulling the piston down the cylinder. Then stick a screwdriver through the plug hole and gently push down on the piston. If you hear and feel a "click" then you likely have slop in the wrist pin bearing.
    The big end of the rods can be checked by measuring the crankpin diameter and the inside diameter of the rod bore. I find that as long as the needles on the big end look good with no galling or bad discoloration from heat, they will usualy work just fine.


    clemg

    US Member - 1 Year (includes $3 online payment fee)
    Replies: 73
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    #82940

    Thanks for the help I’ll try that and let ya know.


    clemg

    US Member - 1 Year (includes $3 online payment fee)
    Replies: 73
    Topics: 20
    #82941

    I tried and found a little play or pop in both pistons.
    Would replacing the needle bearings help the cause or is this normal. I haven’t torn down enough to see rod bearings yet.


    frankr

    US Member - 1 Year (includes $3 online payment fee)
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    #82949

    Those wrist pin needle bearings in 1956 had a nasty habit of the needles getting out and scoring deep grooves in the cylinder walls. Apparently that has not happened to yours or you would see the damage.


    vintin


    Replies: 580
    Topics: 19
    #82951

    Were improvements made in this area in the 1957 35hp RD19?

    Seems I remember it being mentioned in an Outboarder article some years ago.


    adam1961

    Canada Member - 2 Years
    Replies: 366
    Topics: 88
    #82954

    Yes, the 1957 bearings were better and by the time OMC was producing the 28,33 and 40HP motors in the mid 60’s they had them figured out.
    The 1956 bearing is a full complement needle bearing. There are many small needles that make up the full diameter of the bearing. The only thing that holds them in place is the outer race of the bering that is drawn over and crimped around the ends. A full complement bearing is great for high load applications (because there is more bearing surface) but has shortcomings in a high speed application. The needles are more likely to try and run out of square to the inner and outer surfaces.

    For 1957 and up they went to a caged needle bearings. This has gaps between the needles and they are held in place by a cage that can spin withing the end of the rod. This bearing is better suited to high speed. The later bearings are also wider (the small end of the rod is wider) so the later rods wont fit the earlier engines unless you machine the back side of the pistons to expose more of the wrist pin.


    garry-in-michigan

    Lifetime Member
    Replies: 3583
    Topics: 31
    #82972

    One of the ways OMC got the extra five horses in ’56 was by adding needle bearings to the wrist pins. Early testing did not show any problems and so those needle bearing connecting rods were used in the first production run of the ’57 35. One thousand hour wide open testing of the prototypes ( A standard instituted by Ole Evinrude in the 1920s ) had not shown any problems. The first production run of 5000 outboards was made in November for Christmas sales and December boat shows. Sales to Florida and Texas were particularly important because early use in those warmer regions constituted "real world" testing outside of the engineers laboratory. Spring sales were well under way when reports of wrist pin failure hit the company. It was found at high speed the needles circulated and stayed centered, but that in as little as 200 hours of trolling the back and forth rocking wore through the retainer and dropped the needles into the powerhead with disastrous results. The bearing specs were changed and needle bearings with a heavier retainer were used for the rest of the year. Ralph Evinrude had 5000 of the newer 35 horse powerheads sent out to dealers for warrantee replacements of the defective outboards. The dealers were supposed to arrange for this replacement with there customers and letters were sent out to registered owners. It was found many did not read or chose to ignore these letters. Some were pleasantly surprised when the outboard failed five years later to find that they got a new powerhead under there one year factory warrantee . . . 😎


    frankr

    US Member - 1 Year (includes $3 online payment fee)
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    #82974

    Thanks for that lesson in history, Garry. I sort of knew it but not with the detail that you provided.

    Good job, and hats off to you, Garry.


    chris-p


    Replies: 2456
    Topics: 153
    #82977

    Garry,

    Great info!

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