Low idle spits and cuts off

Discussion in 'Bubba's Outboards' started by 01 Mudslinger, Apr 25, 2006.

  1. 01 Mudslinger

    01 Mudslinger New Member

    Messages:
    264
    State:
    Gretna, Va
    i just bought a 76(i think) 16' Thundercraft with a 70hp johnson outboard, motor starts easy and runs great, only problem is if you are at idle or slow forward idle the motor will spit and cut off, it will crank back up and run but if you dont give it more throttle it will spit and cut off again. gets aggravating when tryin to pull in the dock and stuff.if anybody got any ideas i would appreciate it, im new to this boat motor stuff. thanks.
     
  2. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    Hunter look at the top of the carbs and see if they have the black plastic tops on them.
    Wrong plug gap will do that to but I susspect some one has gapless plugs in it.
     

  3. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC
    It could be as minor as a plug change.

    Usually, early in the season, a poor running egine, especially at low idle, would be fuel system related. A visual check for leaks should be done.

    Do you know when the last time the carbs were cleaned or adjusted?
     
  4. kspor

    kspor New Member

    Messages:
    716
    State:
    Wichita Kansas
    I had one do this and it was a small hole in the fuel line. Ran great under throttle, but when I cut it it died. Replaced lines and problem left. Perhaps I just got lucky.
     
  5. 01 Mudslinger

    01 Mudslinger New Member

    Messages:
    264
    State:
    Gretna, Va
    it was my father in laws boat and he had the carbs redone 2yrs. ago i believe, i changed to gapless plugs last weekend and it still does it. i also forgot to mention its got 1 year old gas in it right now i havnt run out completely yet, it had the additive put in to keep it from goin bad. i am gonna check it out this afternoon for leaks hopefully i can get it fixed soon. ill let you guys know what i come up with. thanks again.
     
  6. trnsmsn

    trnsmsn New Member

    Messages:
    1,214
    State:
    Missouri Originally Now I
    I'm Almost Certain That The Additive For Keeping The fuel Fresh Is Only Good For About 6 Months But As Long As It Will Run You Can Drain THe Fuel & Put More additive In It & It May Clear Itself Up, Good Luck.

    Elliot
     
  7. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    Hunter change those plugs back to QL77JC4 and gap them at 40.

    I would do as bob suggested and look for leaks. If that fuel is 1 year old pull it out and get fresh. It may smell good but it don't burn worth a dam in a 2 stroke at 1 year old. Those gapless plugs take alot more fire to fire them then a gap type plug.
     
  8. 01 Mudslinger

    01 Mudslinger New Member

    Messages:
    264
    State:
    Gretna, Va
    well i checked everything over this afternoon, no leaks, no kinks, i got a fresh tank of fuel to run in it. carbs looks good, fuel screen looked good, so hopefully maybe it is just the gas, and i will pick up some more plugs.
     
  9. APD1146

    APD1146 New Member

    Messages:
    176
    State:
    New York
    To Bubbakat;
    Hey Willard remember yesterday or the day before when I asked and you provided a site for a gas gauge problem I had ? The wiring in particular ?
    Well you'll never guess what I found. After rewiring it 7 or 8 times, somehow or another I checked the sending unit in the tank, which as I told you was brand new as well. The wire inside the unit was soldered on the wrong end thus when it was wired to the gauge it read full all the time. I changed the wire to the other end, solder it in place and hooked everything up and presto, I had a working gas gauge. When I went to West Marine tonight for more boat items I told them and they said they would check the rest of the shipment.
    Again thanks for all your help. Tight lines till we talk again.
    John
     
  10. APD1146

    APD1146 New Member

    Messages:
    176
    State:
    New York
    Bubbakat
    Hey Will, just a thought. You talk about boats being a hole in the water to sink money into. Since buying this boat last year I put about $600 into new equipment without counting the 300 feet of wire that went no place I cut out. An not counting all the different connectors and solder used. I probably put in 50 - 60 hours replacing and rebuilding. Just passing it along for other to think about when buying a used boat. PS: The boat was named Black Cloud when I bought it. Do I have to say more. That will change very soon.
     
  11. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    Yeah but john ain't it fun to do. Shucks man I have four and 12 motors.
     
  12. 01 Mudslinger

    01 Mudslinger New Member

    Messages:
    264
    State:
    Gretna, Va
    OK went back out today with fresh gas, still the same problem runs fine under throttle, but at a idle or slow moving idle it will spit and cut off, notice that it seemed like a skip in the motor when you give the throttle to plane out, but once on top it runs smooth and fine. im really gettin aggravated with it, i got new plugs and put them in this afternoon when i got back, gapped at .40, also bought a new fuel line and hooked it up but cant get it to fill with fuel so i hooked the old one back up. think maybe the idle is set too low, i notice the idle screw which i believe is the bottom screw on the right side isnt even touching, maybe i could just bump it up a small hare and that fix it. any new ideas please let me know....
     
  13. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC
    Get the carbs cleaned again and enjoy the rest of the season.
     
  14. 01 Mudslinger

    01 Mudslinger New Member

    Messages:
    264
    State:
    Gretna, Va
    is that something i can do or do i need to take it somewhere, will carburator cleaner help it or hurt it.
     
  15. 01 Mudslinger

    01 Mudslinger New Member

    Messages:
    264
    State:
    Gretna, Va
    i also just read something about adjustin the idleing to the point where it is about to cut off or spits then turned a 1/4 to smooth it out. well it seems to already be at the spittin part so so which screw would i turn and how on a 3 carb engine. just tryin to save a little money if possible, if not i guess ill have to take it in somewheres.
     
  16. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    You can clean those carbs. Its not that hard. Bob put up a good section on cleaning them. http://www.catfish1.com/forums/showthread.php?t=2661


    Just take you a few pictures of the linkage and tear down to aid in the reinstall and go to it. a new set of gaskets and a new needle and seat for all the carbs. Soak them in a good gal of carb cleaner and then blow out all the little holes in it and reassemble.

    You take it in and it will be a whole lot more then the cost of the parts.
    I have soaked them in vinegar mixed with water over night to clean.
    It is a lean condition you are experiencing and one of the carbs is not getting enough fuel to the engine. Build all three because without the experience it is hard to tell you how to find out which one it is.
     
  17. 01 Mudslinger

    01 Mudslinger New Member

    Messages:
    264
    State:
    Gretna, Va
    thanks Bubba, i really appreciate your help, now one more qtn. where can i get teh rebuild kits and a manual to do it, i believe it is a 76 johnson, not sure though, its a 70 something with 3 carbs.
     
  18. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC
    Post the model number to be sure of your engine's age.

    Carb parts can be bought on line at several places or from a Johnson dealer of your choice. I could even send them to you. They'll cost somewhere around 70.00 for all 3.

    A cooling system modification should be done to the older 70 hp engines. Face it now, you've got to spend some money on your equipment, even if you do the work yourself. Cutting corners on maintenance will cost you much more in the long run.

    Get a compression and spark check done and change lower unit oil before going any further.

    Properly cared for, that 70 could be near bullet proof.
     
  19. 01 Mudslinger

    01 Mudslinger New Member

    Messages:
    264
    State:
    Gretna, Va
    where can i find the model #, you talking about for the carbs or the engine, im goin to check for it now, the boat has been taken care of, my father in law has owned it since it was new, just never used it alot the past couple years, like once or twice a year maybe on fishing trips, but was kept in a shop not outdoors, and had the carbs redone 2 yrs. ago i believe, but yea i understand i need to get it back up to par. what involve a compression test, can i get the stuff to do that myself along with the spark test or need to haul it somewhere's, there is a Johnson place here where i live it, if i need to take it to them.
     
  20. 01 Mudslinger

    01 Mudslinger New Member

    Messages:
    264
    State:
    Gretna, Va
    ok, its a '76 where can i get the new carbs carbs from, $70 for all 3 sounds like a better deal than rebuilding em. what about the cooling system, what should be done with it. i really do appreciate all your help on this. this boat is my 1st and it aint nothing special, but for $1000 bucks guess u cant expect much, but i wanna get it fixed up good and running good. thanks. ive attached a couple pictures of the motor and one of the boat, although its under the cover.
     

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