’67 80 HP, seems to starve out with throttle advance, plus rope start link

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Viewing 10 posts - 11 through 20 (of 29 total)

  • billw

    US Member - 2 Years
    Replies: 2071
    Topics: 66
    #207604

    If it makes you feel any better, I have been squirting gas and oil into carburetors for probably almost 50 years and have never had an incident. Reed valves make it pretty unlikely that you will have a blow back. I didn’t make the technique up. It was taught to us by OMC. In small boats where I can both steer and reach the carb, I do it without assistance. Frank has been around longer than I have and has worked on those big old fuel black holes more than me. I am not disagreeing if he says it’s linkage. All I am saying is that the fuel spray test will eliminate any doubt you might have left about fuel supply.

    Long live American manufacturing!

    • This reply was modified 3 years, 8 months ago by billw.
    • This reply was modified 3 years, 8 months ago by billw.

    fleetwin

    US Member - 2 Years
    Replies: 4737
    Topics: 46
    #207607

    Bill’s technique is tried and true, and easy enough to do on this engine, no funky air box/hardware to remove. That being said, safey is key here. You will need an assistant to drive the boat and you must be securely “perched” close enough to the engine so you can spray the carb throats easily. Just put some 50:1 mix in an oil squirt can and spray the throats one at a time at the problem throttle position. Like Bill says, one of three things will happen when each throat is sprayed:
    RPM will decrease indicating the fuel system/carb is functioning OK
    RPM will pick up indicating something is restricting the fuel supply in either the delivery or carb
    RPM will not change indicating those cylinders aren’t firing for some reason
    I think it is safe to say that option three isn’t occurring, but who knows. Keep in mind that you can get different results on both throats. RPM might pick up when spraying one throat, while it might decrease in the other throat. If this occurs, there is some sort of fuel restriction in the carb barrel that increases RPM when sprayed.

    Needless to say, do not perform this operation if you don’t feel relatively safe doing it, perhaps the transom restricts easy access to the carb throats. Have a fire extinguisher ready, although there is no big fire risk here. Backfiring is extremely unlikely.
    I am not that familiar with the sync process on the older V4s like yours, but Frank sure is. I’m pretty sure that the carb has a stop on the throttle shaft that prevents it from going past fully open position but it is worth a look…Perhaps the roll pin is out of the shaft, or the stop boss is broken off the carb body. The symptom you describe sounds like what happens on the newer engines when the sync is off and the carb butterflies can go past the full open position….But again, I’m pretty sure your carb has a stop on the throttle shaft that prevents going past the full open position.
    The only other thing I can think of is that perhaps incoming air is restricted to the engine, or perhaps there is an exhaust leak under the cover. But, I’m pretty sure you have run it with the cover off with the same results….


    frankr

    US Member - 1 Year (includes $3 online payment fee)
    Replies: 6715
    Topics: 51
    #207614

    Wouldn’t it be nice if you could beg, borrow or steal a correct test prop for the motor? Then you could run it WOT without going anywhere.

    EDIT: Since writing that, I got to remembering how scary it is to stand next to a four or six cylinder motor running at 5000 or 6000 RPM. Downright terrifying, actually. I once had a V4 Fat Fifty toss a rod on me at only around 2000 RPM or so. I also knew a man that had a flywheel explode in his face.

    • This reply was modified 3 years, 8 months ago by frankr.

    fleetwin

    US Member - 2 Years
    Replies: 4737
    Topics: 46
    #207624

    I guess I know a big reason I can’t hear anymore as well….Those engines are loud with the air box off…


    Alan


    Replies: 96
    Topics: 55
    #207638

    All replies very much appreciated.

    Wow, pretty exciting to stand next to a motor that threw a rod, or had the flywheel fly apart! Nightmare. Glad nobody got hurt.

    Squirting fuel into the carb while running it sounds like a solid way to narrow down the problem, which would sure help. Although, after 6 unsuccessful attempts, I am running out of people who want to go to the lake with me!

    I’d love to run it in a test tank; that way I could check timing with a light AND give a shot of fuel, without a lake trip. But no dealer in town wants to deal with old motors, or the liability of letting me play in their shop. Which I understand. One time I only made it about 10 steps down a driveway, with a (merely) 15 year old Merc in one hand, and my checkbook in the other before the guy started yelling at me. “Get that thing outta here!!!!!” All red in the face and PO’d.

    I have run it with the cover off, without any improvement.

    The carb does not seem to be opening too far, from what I can see.

    OK, I’ll check the flywheel key today, and look for something loose or cracked.
    Still open to all ideas and wild speculation.
    Much thanks and happy 4th!


    frankr

    US Member - 1 Year (includes $3 online payment fee)
    Replies: 6715
    Topics: 51
    #207644

    Actually, the guy that had the exploding flywheel did get hurt–severely. He lived, but suffered the rest of his life with the after effects of a busted up head.


    Alan


    Replies: 96
    Topics: 55
    #207646

    So sorry to hear that. I’ll keep that in mind and proceed with caution.


    fleetwin

    US Member - 2 Years
    Replies: 4737
    Topics: 46
    #207661

    Franks suggestion about the test wheel is the best/safest method for sure. But, those test wheels are tough to find, and usually command more money than you probably want to pay…The test wheel puts a load on the engine while running in gear without pushing the boat forward. This way, you can tie the boat to the dock, put it in gear and raise the throttle up to check timing/fuel issues, etc…
    I will look on ebay, perhaps there is one priced reasonably…


    fleetwin

    US Member - 2 Years
    Replies: 4737
    Topics: 46
    #207662

    maybe this one will work:
    https://www.ebay.com/itm/305822-OMC-Evinrude-Johnson-50-90hp-V4-Test-Propeller-Wheel-Pin-Drive-1960-s/312799377796?hash=item48d44bb984:g:4dcAAOSwK~ldn3o~

    I don’t have the manual for your engine, so not sure if this is the proper part number….Perhaps Frank knows…


    Alan


    Replies: 96
    Topics: 55
    #207664

    Many thanks Fleetwin, for now and all the other times.

    That one looked like it would work, and the price was great. If that one didn’t, I know I could find one that did.

    But, I seem to remember it was best to run a test prop in an actual test tank, (y’all know better than I). I just have an old city recycling can, (+/- 90 gallon). Don’t think that’s enough to provide sufficient circulation. Or something. The water would heat up pretty fast at 5,000 rpm, maybe. Love to be wrong on that. And as I say, no shop wants to let me play. Given liability / insurance issues, I understand.

    So, the inline fuel filter I put in isn’t restricting it at full throttle, right? I took it off and blew it out; didn’t seem restricted. And it’s an actual OMC marine fuel filter, right side up even.

    Felt like I got just a bit of leakage when I vacuum tested the male, motor fuel connector, (303600). Hard to tell; just wrapped one end w/ electrical tape and sucked on the other. Not very scientifical. But did seem to have a tiny bit of leakage. I’ll probably replace.

    As recommended, I guess I need to sit in the back and squirt some fuel mix in it while someone drives. I agree, that should differentiate.
    Appreciated.

    • This reply was modified 3 years, 8 months ago by Alan.
Viewing 10 posts - 11 through 20 (of 29 total)
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