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

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  • frankr
    frankr


    Replies: 5234
    Topics: 48
    #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.

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    Alan

    US Member - 1 Year
    Replies: 93
    Topics: 51
    #207646

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

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    fleetwin

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

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    fleetwin

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

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    Alan

    US Member - 1 Year
    Replies: 93
    Topics: 51
    #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 1 month ago by AvatarAlan.
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    billw

    US Member - 2 Years
    Replies: 1246
    Topics: 40
    #207672

    Can’t you leave the engine cover on and squirt the gas in the carb through the little front door? If the flywheel explodes and comes through that and kills you, your days were up, anyway. Come to think of it, can I do the test FOR you? Then I won’t have to watch the TV news anymore.

    Long live American manufacturing!

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    Alan

    US Member - 1 Year
    Replies: 93
    Topics: 51
    #207678

    Yeah, don’t get too much of that “news” on you! That also poses a risk to your head.

    I’m not worried about the actual testing, really. It can be a drag to make the two hour round trip to the hot, crowded lake for 20 minutes on the water. For the 7th time. Not so much for me as for whoever else goes with. Lately it’s ended up being my 84 year old Dad who has recently recovered from a broken knee He’s been a great sport so far and will again, I’m sure.

    From what I’ve seen of flywheels disintegrating, I don’t know that the fiberglass motor cover would be much protection at 5K RPM. Hope never to know!

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    fleetwin

    US Member - 2 Years
    Replies: 3303
    Topics: 49
    #207679

    Running the test wheel on the boat in the water actually works best… Usually, water just splashes out of the test tank causing the engine to ventilate, and RPM to fluctuate quite a bit….This will just add more confusion to your issue. I realize that getting the boat to the lake is a pain, but it is the best test method…

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    Alan

    US Member - 1 Year
    Replies: 93
    Topics: 51
    #207687

    Advice appreciated.
    I looked back, and Dan says the part number for the test wheel I need is 379215.
    I guess I’d just have to back it into the water; wouldn’t necessarily even have to take it off the trailer. In a way that wouldn’t block the dock / ramp, of course. Don’t want to be that guy.
    That way, if I gave it a shot of fuel and the RPMs jumped up, I wouldn’t get any 25 mph surprises.
    I’ll report back if / when I learn anything.
    Thanks to all.

    frankr
    frankr


    Replies: 5234
    Topics: 48
    #207691

    Looks like a lot of discussion has taken place since my last visit, so let me clear up a couple of things.

    The flywheel that blew up was on a race engine. The guy had machined off a bunch of metal to lighten it. Live (maybe) and learn.

    Test props. They work by the fins grabbing water and flinging it against the outer rim by centrifugal force. The faster you turn it, the more water fling. The result is forces that are working against themselves, like trying to pick up a chair while you are sitting in it. Also, the fins are angled and do provide a bit of forward thrust like a regular prop. This is necessary to keep it in solid water and not just sit there making a hole to cavitate in. The forward thrust in small in a 6 hp, but a big V4 moves a lot of water. No way in hades can you run a V4 at WOT in a trash can, test prop or not. Likewise, test props are matched to horsepower. For instance, a 28hp is different than a 35 hp, which is different than a 40hp, although they all fit the same shaft. And yes, they work best with the boat launched and tied to the pier. Since our shop was land-locked, I had a full set of test props up through 200 hp when I was twirling wrenches for a living. And a large professional test tank. Even so, I couldn’t run a 200 in it at WOT. Too much air mixed with the water.

    Posting the last list that I have.

    Test-Props-2

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    fleetwin

    US Member - 2 Years
    Replies: 3303
    Topics: 49
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    Alan

    US Member - 1 Year
    Replies: 93
    Topics: 51
    #207775

    Great info; very much appreciated.
    I feel a bit better knowing that the flywheel which flew apart had been modified. I like modifying stuff, and feel bad for the guy.
    But I’ll be a little less nervous when running the test prop I just bought. While I’m sitting back there squirting fuel at it at 4,800 RPM.
    It will be nice to narrow down my issue to either fuel or spark, and I’ll report back with that info.
    Thanks again;
    Alan

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    need2fish

    US Member - 2 Years
    Replies: 123
    Topics: 11
    #208301

    I’m with timing as the problem, but I have to ask: I know you mentioned gaskets, but is it possible you have an air leak at the carb to manifold mating or manifold to reeds mating ?

    Or a stuck / bent reed? One bent reed may not cause blow-back from the crankcase, but will lean out the charge.

    Is the fuel pump original to the motor ?

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    Alan

    US Member - 1 Year
    Replies: 93
    Topics: 51
    #208321

    I’ve replaced and reinspected the carb to manifold gasket several times, but not the manifold to reeds surface. I’ll scrutinize that.
    I had no idea a bent reed would lean it out; I’ll put that on my radar for sure. This would explain the mysteriousness.

    The fuel pump body appears to be original, and I’ve replaced the check valve once and the diaphragm twice. When I disconnected the fuel line from the carb and cranked it over, it put out (what seemed to me) plenty of fuel.

    I very much appreciate the expert advice, and will keep ironing out the ignition. I did verify that the flywheel hasn’t slipped, and I’m sure the belt timing is OK.. Next step is to make sure the points are breaking at the right time. After that I’m not sure where to go with the ignition.

    I did get a test wheel, and will report back as soon as I can run it with that. I hope to narrow my focus.
    Many thanks;
    Alan

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