1957 Sea King 12HP won't run right

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This topic contains 24 replies, has 9 voices, and was last updated by Avatar fleetwin 3 days, 23 hours ago.

Viewing 10 posts - 16 through 25 (of 25 total)
  • labrador-guy
    labrador-guy
    US Member - 2 Years
    Replies: 174
    Topics: 25
    #173169

    Couple things, you stated in your original post that you needed to keep the choke closed in order to keep the motor running. Did you check the screen in the fuel tank? Sure sounds like lack of fuel to the carb to me. Also remember if you coat the float with glue or whatever. It might not float the way it should. Coating makes the float heaver. I have one of these 12hp babys and it runs great. Little on the heavy side but aren’t we all!

    dale

    seakaye12
    seakaye12
    US Member - 1 Year
    Replies: 361
    Topics: 97
    #173174

    I have a 7.5HP Fleetwin that has similar issues. I was about 99% sure it was a carburetor issue but when I swapped carbs from a great running Fleetwin nothing changed. Mine runs “ok” above idle but seems incapable of drawing fuel through the idle circuit of the carb. Frustrating. Maybe your solution will be my solution.
    One thing I could suggest you try: Have a close look at the needles. Are they the correct ones? I once had a 12HP like yours that ran terrible and when I swapped carbs things improved. Looking at the original carb I saw that someone had replaced the slow speed needle with an incorrect one. It screwed in but was not long enough and was of the wrong taper. Hard to tell without another carb to compare against as they have no part numbers.

    • This reply was modified 6 days, 9 hours ago by seakaye12 seakaye12.
    • This reply was modified 6 days, 9 hours ago by seakaye12 seakaye12.
    • This reply was modified 6 days, 7 hours ago by seakaye12 seakaye12.
    Avatar
    huntleybill
    US Member - 1 Year
    Replies: 208
    Topics: 79
    #173199

    OK…I took the carb back apart. It has packing in it but I put 1 extra (total 3) in each needle. I replaced the float ( just cuz I had a new one on the shelf) I don’t think the old one was bad so I’m going to save it. I also blew compressed air through all the holes. I made sure the vent hole was clear. I put it back together and ran the motor. I am attaching a video. Basically, it starts right up. It runs rough and as I turn the high speed needle in the motor starts to smooth out and pick up speed. Just as it smooths out nicely, it will buck and kick and dies out (approx 1 min in the video). It idles ok but the low speed needle is about 2 turns out

    Maybe I just need to get it out on the lake and run it!! What do you think?

    Avatar
    dave-bernard
    US Member - 2 Years
    Replies: 827
    Topics: 10
    #173201

    you need a test prop to set the high speed in the tank. and you need a fan to get the exhaust away from the carb. do it on the boat run it rich then dial it toward lean till it runs to lean then set about 1/2 way in between . then you are about set. then set the idle the same way. hope this helps.

    Avatar
    bayham3261
    US Member - 1 Year
    Replies: 28
    Topics: 4
    #173204

    If the float is set correct and looks ok I wouldn’t think that it is an issue. So are you still running it with 1/2 choke? I’ve had similar symptoms before of a failing ignition… but that wouldn’t explain the need for choke. If it isn’t a big deal i’d get some fresh gas and take it for a spin… as long as you have a way of getting back to the dock! lol… I’ve had good luck with seafoam gas additive to clean up carbs and combustion chambers.

    A little information is a dangerous thing!

    Avatar
    huntleybill
    US Member - 1 Year
    Replies: 208
    Topics: 79
    #173205

    thanks Dave. I have the motor in reverse for the video. That way, I have a load on the motor. Also, there is a fan running in the background blowing on the motor.

    The choke is wide open for this test as you can see in the video. I think it is running better but certainly NOT as it should.

    frankr
    frankr
    US Member - 1 Year
    Replies: 3996
    Topics: 43
    #173211

    That motor is responding to both high an slow speed adjustments. It is lean sneezing if you twirl the knob to the right and 4-stroking if you twirl it too the left. Speaking of twirling, that is what you are doing. Those things are sensitive and require minor dialing to get it right. I don’t think there is anything wrong that motor that won’t be corrected by putting it on a boat and adjusting the carb properly. High speed knob first at WOT, then slow down and do the slow speed knob.

    Avatar
    huntleybill
    US Member - 1 Year
    Replies: 208
    Topics: 79
    #173214

    ok…thank you. As soon as we get a day warm enough to go boating, I will run the motor and re-adjust it.

    olcah
    olcah
    US Member - 1 Year
    Replies: 293
    Topics: 65
    #173364

    I would think 3 packings/needle would be enough but it looks like the packing nut on your slow speed needle is all the way in. If so put in yet another packing. It just might not be sealed.

    Avatar
    fleetwin
    US Member - 2 Years
    Replies: 2531
    Topics: 29
    #173405

    Not that familiar with the Sea King variations on the original OMCs, except to realize that they use a mix of parts from different year OMC models…So, my first question is was this engine originally set up for a pressure tank? In other words, is the pressure tap on the intake manifold capped off with a plug? What hose am I seeing with the bolt stuffed in it? If the engine has the nipple in the manifold for the pressure tank, and there is a leak, it will do exactly what yours appears to be doing…..Does this engine have a fuel pump on it? It must if you are using a single line tank. A bad fuel pump could be causing an air leak or lean running condition, try pumping the fuel line primer bulb while the engine is misbehaving to see if that helps….
    My other question is whether your carburetor has that pesky threaded sleeve for the low speed needle that tends to turn inside the carb body when you attempt to make low speed adjustments. I too noticed that the low speed packing nut is threaded pretty far in, I would add another packing washer and perhaps one of the plastic washers used on later models…The packing nut must be tight enough to hold the stupid sleeve in place or you will think you are making low speed adjustments, but are actually doing nothing.
    Finally, I agree, you are over doing it with the large adjustments on the needles….Set the initial adjustments, make sure the packing nuts are good and snug, then take it to the water and try it out on a boat. Dial in the high speed first, then fine tune the low speed needle. One final thought, are the set screws tight holding the knobs to the needles, perhaps the knobs are slipping on the needles adding to the confusion/frustration….

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