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    need2fish

    US Member - 2 Years
    Replies: 123
    Topics: 11
    #208369

    I saw a Kijiji ad for a clean, low hours 1973 Johnson 4hp model 4R73C — It’s a descendent of the 3hp JW weedless. Carb was done, coils and impeller replaced, so at $120 it was a good fit with my budget.

    The seller said he was having some driveshaft wear issues; i have 2 basket case JW’s so i grabbed the lower unit of one and went to see it. I’m looking for a take-me-home for my pontoon boat — my Mighty Mite has grown Mighty Cantankerous in it’s old age and needs to be retired.

    I was confident I could use my driveshaft to repair the 4hp and after a quick compression test, sealed the deal and brought the little cutie back home.

    After disassembly I found the problem isn’t with the driveshaft, it’s with the crankshaft receiver. All three of my driveshafts grind and spin in the receiver socket. The socket is ruined and the splines of all 3 shafts have been gnawed on.

    It appears my only choice is to find a used crank in good condition…

    My questions are 1) Is this a known problem with the JWs , their Evinrude equivalents and descendents ? and 2) If I find a decent crankshaft, how do I make sure it doesn’t degrade again (and I promise i will replace the upper driveshaft o-ring) ?

    Tubs
    Tubs

    US Member - 1 Year
    Replies: 3070
    Topics: 169
    #208371

    • This reply was modified 4 weeks ago by TubsTubs.
    • This reply was modified 4 weeks ago by TubsTubs.
    • This reply was modified 4 weeks ago by TubsTubs.
    • This reply was modified 4 weeks ago by TubsTubs.
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    need2fish

    US Member - 2 Years
    Replies: 123
    Topics: 11
    #208379

    Hey, did you take one of my driveshafts ? 🙂

    frankr
    frankr


    Replies: 5234
    Topics: 48
    #208381

    Agreed, there a ton of those 3hps out there with stripped splines. It’s because people leave the o-ring out, and water gets into the steel splines of the crank and they rust away. Doesn’t take very long in salt water either.

    bobw
    bobw

    US Member - 1 Year
    Replies: 1070
    Topics: 41
    #208382

    Leaving the shaft O-ring out during reassembly can be fatal to any motor. During disassembly of my 57 Fastwin, I found the driveshaft O-ring missing or long gone. Here’s what the crankshaft and driveshaft splines looked like.

    06-Driveshaft-Splines-Boogered

    25-Crank-Spllnes-No-Good

    Bob

    1954 Johnson CD-11
    1956 Johnson RD-18
    1958 Johnson QD-19
    1959 Johnson QD-20
    1957 Evinrude Fastwin 18

    "Every 20 minute job is only a broken bolt away from a 3-day project."

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    frankr
    frankr


    Replies: 5234
    Topics: 48
    #208393

    Agreed, almost any motor. Some such as Chryslers and Scott’s didn’t even have an o-ring but needed one. Others didn’t have one but didn’t really need one. I was really disappointed when OMC started putting the o-ring in the crank instead of on the drive shaft.

    • This reply was modified 4 weeks ago by frankrfrankr.
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    jcrigan

    US Member - 2 Years
    Replies: 141
    Topics: 16
    #208463

    Would a 3hp crankshaft from a 1964 motor work? I may have one of those.

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    fleetwin

    US Member - 2 Years
    Replies: 3303
    Topics: 49
    #208466

    Yes, depending on the usage, spline wear is not uncommon. I get so frustrated when I see this critical procedure overlooked by so many techs. The oring needs to be in place and the side of the splines must be generously coated with the OMC moly lube. The 5-8hp models seem prone to this disaster also, even with all the various changes in an attempt to protect the splines…The beauty of these engines is that it is so easy to remove the gearcase yearly (no shift rod connector) and relube the splines. This issue is even more severe in salt water. The gearcase needs to come off on all outboards at least every other year to clean/relube the splines and do the water pump. You don’t want to witness the carnage of sawing a V6 apart in order to remove the gearcase.
    Oftentimes I will use a spare driveshaft sprayed with WD40 (unless it pulls out of the gearcase easily) to work in and out of the crank splines in an attempt to clean out some of the rust/crud that is building up…Then I lube those driveshaft splines and do it again before actually reinstalling the gearcase.
    I haven’t seen a way of saving the crankshaft on these engines…Your 4hp does not have a lower seal, but the crank has a little slot that helps lube/protect the lower journal and bushing. Cutting a slot in the crankshaft defeats this function. I don’t think the 3 and 4hp cranks were the same, so the crank from the 64 3hp won’t help. I’m assuming you have already bought this engine, so you will need to look for a decent affordable used crank/powerhead. I’m sure you will inspect the splines closely, measure the rod journals also. These little engines had a habit of pitching the rods, don’t be fooled by journals that have been “cleaned up” with crocus/emery cloth. The driveshaft will need to be replaced also.
    The 1976 was the first OMC to have the oring positioned in the crankshaft. Good and bad to this design. Seems like the oring is less likely to come out of the crank groove than it is to be pushed out of the driveshaft groove during installation. But, the powerhead has to come off to inspect or replace the orings positioned in the crank….

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