1966 Evinrude 18hp… cough sputter cough!

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  • omcbeaulieu86


    Replies: 11
    Topics: 9
    #1829

    I recently acquired an 18HP Rude that is in very good shape. I cleaned the carb, changed the coils, and it fires up. I went to the lake and as soon as I gave it gas, I had very little power. It bogged down quite a bit. The strange thing though, was that while giving me little power, it would suddenly KICK in and give me a micro burst of what sounded like and felt like full power. This only lasted a split second and was intermittent as it would occur from time to time. During this micro burst of power, the pitch changed to a higher pitch and it sounded like what it should sound like. It doesn’t like to idle low very well either. It wants to backfire, and rides quite rough during idle. It also backfires often enough when I am trying to pull start it.

    I will let you know what I did do…

    Cleaned the carb
    New coils
    fuel pump is operational

    I had difficulty setting the low speed needle because it was hard to tell when it was seated all the way down due to the packing nut. I have the packing nut completely in, and the needle completed in, taken out a full turn or so. I find the adjustment needle has a little wiggle room when it is in the carb.

    One more question, when I adjust the points, it says TOP on the cam lobe. Does that just mean that is the TOP side of the lobe, or does it also mean that is where my points need to be open the most at that point?

    Thanks for your help! I want this motor up in running. It was a sweet find for 150 bucks!

    -OMCBeaulieu


    optsyeagle


    Replies: 29
    Topics: 1
    #18687

    Usually when you get a low power motor that suddenly pops into action for you and then bogs again, you are experiencing one cylinder intermittently cutting in and out. If it is not working at all, I would do a cylinder drop test to find out which one is not working. To do so, simply fire up the motor, let it warm up, bring it to a fast idle and with a pair of insulated pliers pull one spark plug boot at a time. If the motor dies, then you now know the other cylinder was never firing or is very weak.

    If I had your issues, I would want to do an external spark test to verify that each cylinders ignition can jump a minimum of a 3/8" gap and I would want to verify that the compression on both cylinders was even within 5 psi.

    Now you talk about backfiring. When you changed the coils is there a chance that you mixed up the wires going to the two spark plugs. I would think that if you did, you would not get either cylinder to run well but you might get one or both to want to backfire. Since it is backfiring, you could check that.

    When setting the points, bring the point rub bar to where the flywheel key is to set them. The word TOP is just to indicate that if the cam comes off it cannot go back on either way. It must go on with the word TOP facing up. That is all that word is for.

    I am not sure why the packing nut would prevent you from turning in the slow speed needle unless it is too tight. The packing nut should be loose enough to allow you to turn it either way but snug enough to ensure it does not turn on its own.


    Mumbles


    Replies: 5764
    Topics: 298
    #18688

    Did you clean or replace the points, condensers and spark plugs? If points are cleaned, they also have to be polished to a mirror finish and cleaned with lacquer thinner or acetone to degrease them so they operate properly. Sometimes it easier and quicker to install new ones.

    Bad plugs will cause a miss when the motor is being accelerated. So will bad points and capacitors. Backfiring is usually caused by a lean running condition which can be caused by a wrong carb adjustment or air leaking into the motor thru worn carb throttle shaft bushings or a worn top seal on the crankshaft. New packing washers on the needle will help to hold it in place and prevent any air leaks. TOP on the points cam identifies the top side of the cam itself for installation purposes. The points are at their widest opening for adjustment in this general area. I just do a visual for their widest opening before setting them at 0.020" if I don’t have a proper timing tool for setting them. Hope this helps some.


    chris-p


    Replies: 2456
    Topics: 153
    #18690

    You need to tighten the packing nut some more, to let you to seat the low speed needle. It threads into a bushing that can free spin in the hole, so you may be MUCH richer on the needle setting than you think. Tighten the nut, seat the needle, then back it out 1.5 turns.

    DId you torque the flywheel nut after installing the flywheel? You MUST. And, the taper must be perfectly clean. I use acetone on the tapers.


    fleetwin

    US Member - 2 Years
    Replies: 4737
    Topics: 46
    #18725

    Like everyone says, sounds like the engine is running on one cylinder, the other kicks in occasionally which explains the change in "pitch" and power for a second. Hopefully, this is just an ignition problem, could be something as simple as a bad plug. Just cuz the parts are new, doesn’t mean they are any good.
    Another relatively cheap diagnostic tool are those inline neon spark testers, you can get them at most parts stores/Sears/Harbor Freight.
    Run the engine with two testers inline between the plugs and coils. Have an assistant drive while you monitor the testers, probably easier when the sun is going down. Keep in mind that a bad plug could cause the tester not to light as well.


    jeff-register

    US Member - 2 Years
    Replies: 1564
    Topics: 54
    #18741

    My 1958 Johnson 18 had missing & backfiring when I bought it too. Many items already may very well be the problem but was the magneto seem covered with oil. My top seal had gotten very hard & not sealing very well spraying oil on the magneto. With your needle jets not staying snug you also may have a vacuum leak causing the motor to run in a lean condition causing missing. Have you removed the spark plugs to see how they are running? Should be a dark tan to be running correctly. Please try to get the missing repaired as it causes the motor to be out of balance. Let us know how you do.


    omcbeaulieu86


    Replies: 11
    Topics: 9
    #18769

    Thanks for the help! I will definitely take a closer look at the spark plugs, try new ones, and check compression. I recall it being very good but then again, I can’t remember how close in PSI each cylinder is.

    I will clean the points as well and check to make sure the spark runs hot. I will keep this thread posted on any progress. Thanks again for the awesome detail in your replies!

    -Marc


    omcbeaulieu86


    Replies: 11
    Topics: 9
    #18770

    ps: What should I torque the flywheel at?

    Thanks


    phil-b


    Replies: 463
    Topics: 28
    #18777

    40-45 foot pounds, make sure the taper and the inside of the flywheel are clean of any oil/grease

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