1954 big twin

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  • Tinman

    US Member - 1 Year (includes $3 online payment fee)
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    #184977

    I got home and checked compression. 85 top and bottom. Is that good enough to proceed? Not sure where those # should be on a 25 hp. And they may improve once its running.


    Tinman

    US Member - 1 Year (includes $3 online payment fee)
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    #185017

    Does anyone know if the compression numbers are ok? Thanks.


    bobw

    US Member - 1 Year (includes $3 online payment fee)
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    #185021

    85 is a little low but it should run. I’d run it with some fresh gas and oil and some Engine Tuner or other decarbon product and see if that might loosen up some sticking rings and let the compression come up some. You may also have a bad head gasket.

    Bob

    1937 Champion D2C Deluxe Lite Twin
    1954 Johnson CD-11
    1957 Evinrude Fastwin 18
    1958 Johnson QD-19
    1958 Johnson FD-12
    1959 Johnson QD-20

    “Every 20 minute job is only a broken bolt away from a 3-day project.”
    "Every time you remove a broken or seized bolt an angel gets his wings."


    fleetwin

    US Member - 2 Years
    Replies: 4737
    Topics: 46
    #185022

    Well, 85PSI seems a little low for that engine, but you are cranking it by hand, which is tough….I would definitely rig up some jumper cables to you can crank it with the electric starter… Originally, this was a 6 volt system, but who knows what is in there now…Have a look at the starter, perhaps it will say. You can use a 12 volt battery on the 6 volt starter, provided you don’t crank it for too long a period. But, using the 12 volt battery on the choke solenoid will damage that part. Sounds like this engine is in nice original condition, all the wiring/junction box is there also? If so, you surely don’t want to damage any of those pieces…An electric start big twin from that era is quite a bit more rare than the standard recoil model. For must of us old cranks, the electric start is a much needed option….
    So, recheck compression using the electric starter…
    Pull the flywheel, do you have the OMC puller unit? Please don’t attempt this using some alternative puller, damage and injury can result. The ignition will surely need to be completely serviced unless someone has been in there recently…
    Drain/refill the gear lube? Is the gear lube relatively clean, free of water? Older lubes were pretty dark in color so that is normal. Milky colored gear lube is an issue, raw water spells trouble. You should probably pull the gearcase and replace the water pump impeller.
    The carb should be disassembled, cleaned and rebuilt as well, unless there is evidence that someone has done this work and used more up to date gaskets/etc. Finally, do you have decent pressure tank? Open the cap, have a look inside…A badly fouled/rusted tank is useless….
    Feel free to post pictures with any questions you have, makes it easier to understand what you have so we can provided more useful advice/answers…

    • This reply was modified 4 years, 5 months ago by fleetwin.
    • This reply was modified 4 years, 5 months ago by fleetwin.

    Tinman

    US Member - 1 Year (includes $3 online payment fee)
    Replies: 355
    Topics: 77
    #185037

    It’s all original. 6 volt. I have a 6 volt battery so no worries there. Going to haul it to the garage soon to start looking it over real good. I also have many clean pressure tanks so that’s never a problem. Pick up every one I can find!! It is a bear to eope over by hand so I will hook up the starter and check again. Did they originally come with brass props or is that an aftermarket item? Sorry for less than good pics. Motor is in my barn.

    IMG9551821

    IMG9551841

    IMG9551851

    IMG9551881


    fisherman6

    US Member - 2 Years
    Replies: 1702
    Topics: 34
    #185055

    Nice Motor. It is a little nicer than mine which has faded to nearly bare aluminum on the cowl. I have about 90-95 psi compression with mine and the cylinders have seen better days. I would pull the exhaust covers and take a look inside to see how yours look.

    Mine will not stay running and I’m almost 100% convinced mine is due to water intrusion through the exhaust baffle plate. I have not taken the exhaust cover off yet to see how the plate looks but I’m betting there are holes in it. Hopefully yours has not suffered a similar fate. I plan to do a complete rebuild on mine at some point unless I stumble upon a powerhead in much better condition. It is a great motor that I want to run someday.

    I have two ’54 Johnson 25s. An RD-16 and an RDE-16 that are both fantastic runners and probably my favorite tiller motors to run on a boat. Well worth putting the work in to get it going. They are a blast.

    -Ben

    OldJohnnyRude on YouTube


    frankr

    US Member - 1 Year (includes $3 online payment fee)
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    #185059

    They came with an aluminum prop


    fleetwin

    US Member - 2 Years
    Replies: 4737
    Topics: 46
    #185064

    Looks like a beauty for sure…Do you have the wiring harness/junction box/switch panel? If so, you really have something special there. Don’t know if I would use the brass prop, they put more strain on the gearcase and clutch dog….


    Tinman

    US Member - 1 Year (includes $3 online payment fee)
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    #185076

    I do not have any of the wiring harness, box or switch panel. And Ben I have seen your videos of your 25 hp johnsons. Cool looking and running motors! I have a very nice qd-12 10 hp that I want to fix up also. Probably start on it after the 25 hp. But I really want to tackle this 25 now that I have a boat that will handle that many horses. Bryan.

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