92 Johnson 40 HP Carb rebuild

Discussion in 'Bubba's Outboards' started by bigflathunter, Apr 8, 2008.

  1. bigflathunter

    bigflathunter New Member

    Messages:
    90
    State:
    Lawrence, KS
    First of all, thanks for the nice tutorial with pictures on carb repair. It works out nicely that my motor is a 92 40 horse, and the one in the tutorial is a 92 70 horse, both Johnsons, so the carbs are almost identical.

    First, my problem. The motor is very hard to start, if it will start at all. Gas/oil mixture bubbles up out of the water after a few seconds of cranking. I checked for spark, and spark is good, and it's getting air as I manually held it at WOT with the cover off to try and get it to fire at the boat ramp. So my next step was to rebuild the carbs. I got two OEM carb kits from the marina and am following your instructions in the tutorial. That's where I realized my problem might have just been an adjustment.

    My question is about the low speed adjustment screw, and the directions with picture 9 in the tutorial. It says that the "common" adjustment is to lightly seat the screw all the way down, then back out 1 1/2 turns. I tightened mine down to where it was seated so I would know how far out it was to begin with. That way I could put it back to the same place when I put it back in. It took 2 3/4 turns to seat it lightly. Could this be why it was flooding out so bad, or should I leave it at this adjustment when I reassemble everything?

    If there is any more information you need I'll be happy to provide it. Thanks in advance.
     
  2. AwShucks

    AwShucks New Member

    Messages:
    4,532
    State:
    Guthrie, Oklaho
    It seems to me that on Johnson/Evinrude carbs you can't adjust the low speed idle... it is all perset. And for sure I don't remember a needle spring adjustment as your referring to. I'm wondering if your initial problem was not some of the linkage adjustments on the motor/carbs. The manual has the steps and if your off slightly, your motor will act like it is ready for the undertaker.
     

  3. bigflathunter

    bigflathunter New Member

    Messages:
    90
    State:
    Lawrence, KS
    Everything seemed to be working fine as far as linkage goes. At least just by looking at it. I know it does have the needle and spring adjustment, just as shown in the picture in the tutorial. I already talked to the guy at the marina about a service manual, they would have to order it in. That screw seems to be the only adjustment on the carb itself. There is an adjustment screw on the linkage for idle speed though, I believe.

    When I would try to start it, it wouldn't even remotely sound like it wanted to fire. I had to hold the linkage at WOT, and then I'd only get about 3-5 puffs of smoke and it would die.
     
  4. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC
    Not all, but most will adjust to 1 1/2 turns.

    If your needle has a very sharp point, I've found those to be the ones that adjust to near 1 1/2 turns out.

    Some low speed needles have a dull rounded tip, Those I've found to need closer to 2 1/2 turns out.

    Once you reassemble your carbs, you'll find out for sure as you try to start it. Be sure the choke is working properly.
     
  5. bigflathunter

    bigflathunter New Member

    Messages:
    90
    State:
    Lawrence, KS
    The needles are the long pointy type. I'll adjust to 1 1/2 turns, then I'm going to take it and try it this evening to see what happens. Thanks for your help.
     
  6. bigflathunter

    bigflathunter New Member

    Messages:
    90
    State:
    Lawrence, KS
    Also, another question. I have to replace a section of fuel hose that goes from the top carb to the bottom carb. The hose that came off is 5/32" I.D., but I can't seem to find anybody who sells it or who will even order it for me since I need only about 8" of it. Would it be alright to replace it with 1/4" I.D hose, which is available locally? It's only 1/32" smaller, but I don't know if it will starve the engine for gas. Thanks.
     
  7. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC
    Sure, give the 1/4" line a try.
    You can get that 5/32 from a Johnson dealer.
     
  8. bigflathunter

    bigflathunter New Member

    Messages:
    90
    State:
    Lawrence, KS
    About the choke, I can't seem to figure out how to even tell where the choke control is, if it even has one, so I guess I won't know if it's working or not :eek:oooh:. Model Number J40TLENM 1992. I attached a picture of my controls. When I move the lever on top up, it opens the throttle up slightly to speed up the idle.

    First and second pic show lever in up and down position, then the third picture is what the butterfly looks like when the lever is up.
     

    Attached Files:

  9. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC
    That's the nuetral warm up lever on the control box.

    You don't have a choke. You've got a primer system.

    Put the key in the ignition and push in on the key. Listen for a clicking sound. That's the primer solenoid opening and allowing gas in at the rear of the carbs.
     
  10. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    I love those primer systems. Bob paul I am very glad you grabed a hold of this one.
     
  11. bobs bait

    bobs bait New Member

    Messages:
    1,338
    State:
    north carolina
    i had a 40 merc with the electric choke mind was hard to start after listening to the selnoid click thought it was working took it to the dealer found out the switch was working but not opening the choke there was a loose wire when he pushed it together worked great cost me some money i would of never thought about that as i could hear the selnoid working bob
     
  12. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC
    Toatally different type of solenoid.
     
  13. bigflathunter

    bigflathunter New Member

    Messages:
    90
    State:
    Lawrence, KS
    Well I tried to get it running tonight. I had the low speed screw adjusted to 1.5 turns out, primed it, and had the lower unit in a big trough full of water in the driveway. It started right off the bat, then died about 15 seconds later. It took manually holding the throttle open (farther than the adjustment knob on the control box would let me) to get it to start again. Then it ran pretty well, but was smoking like it was getting waaay too much gas. So I tightened the screws down to 1 turn out and it started right up, and didn't smoke nearly as bad. Any ideas as to why I might be getting this much smoke? I'm going to put a new set up plugs in tomorrow.

    I posted a link to a video on youtube of the motor running after I got the low speed screw adjusted to one turn. It's hard to see the amount of smoke there, but you can see some coming out of the exhaust and some bubbling up out of the tank in the bottom of the video.


    http://www.youtube.com/watch?v=WnnvD81Pp-c
     
  14. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    What color was the smoke? White or Blue. Also do a compression check.
     
  15. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC
    Check to see that the red knob on the primer solenoid is in the right position, or just turn it 90 deg's. An often overlooked item. If it gets worse then turn it back to where it was. Even in the partcially opened position, it'll dump to much gas to the carbs.
     
  16. bigflathunter

    bigflathunter New Member

    Messages:
    90
    State:
    Lawrence, KS
    Looks to me like the manual valve is in the correct position. Here is a picture of it. I haven't messed with it at all since I've been working on the motor.

    When I push the key in, I don't get a click from the primer solenoid. Also, when I squeeze the primer bulb, I could see fuel being squirted into the carb when I opened the butterfly valve prior to replacing the cover that goes over the carbs. Sounds to me like the solenoid is stuck in the open position.

    This happens whether the battery is hooked up or not, so I'd imagine it isn't the ignition switch shorting out and giving the solenoid a constant open signal. Does this sound right?
     

    Attached Files:

  17. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC
    No it doesn't sound right.

    You need to do the carbs again. When the primer bulb is pressurised the float in the carb forces the needle to shut off gas to the bowl. If your still getting gas into the carb throat, the needle isn't seating.

    Your right in thinking it's trying to run in a flooded condition, and the needle not seating properly, is why.
     
  18. bigflathunter

    bigflathunter New Member

    Messages:
    90
    State:
    Lawrence, KS
    Last night and today I had a chance to do the carbs again. This time, I double checked that the floats were adjusted properly so the needle would seat when the bowl fills up. Then, after reassembling the carbs, I took a clean piece of fuel line and hooked it up to the main fuel inlet near the bottom of the carb body. I held the carb right side up, and could blow through. Then I turned it upside down and tried to blow through, and couldn't, so the needle must be seating. I then reassembled and tried the primer bulb again, and got the same result.

    Next thing I did was trace where the gas comes from. There are three lines that feed each carb, one down near the bottom of the carb body (main filler line for the bowl?), one line at the top that connects the two carbs together (what does this do, by the way?), and a small one on the top that appears to be the primer line. It goes directly through the carb body to a nozzle that angles towards the intake manifold. This is where the fuel is squirting in when I pump the bulb. I traced that line back to the primer solenoid.

    I also looked to see where the VRO unit sends fuel. It sends one line to the top carb, one line to the bottom carb, and one line to the primer solenoid.

    From the primer solenoid, two small lines go out, and each one feeds one of the small nozzles on the top of the carbs.

    I tried pinching off the line that feeds the primer solenoid from the VRO with a pair of pliers, and pumped the bulb. Gas did not squirt into the primer nozzle on the top of the carb, instead it squirted into the main bowl line on each carb.


    What does this all mean?
     
  19. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC
    Aaron, I had a problem a few yrs back with that very same carb set up. I didn't fix it then, but another fella did. When I asked him what the problem was, all he said was, the carbs weren't done right:sad2:

    I don't have access to the manual covering that engine, and I need to refer to it. No gas should squirt in the carb throat, by squeezing the bulb.

    Check the pos, and neg to that primer. If it doesn't make the clicking sound, which is when it opens to let fuel bypass, then it's possible it could be stuck open. Very unusual for it to do that.
     
  20. bigflathunter

    bigflathunter New Member

    Messages:
    90
    State:
    Lawrence, KS
    I took it off and wired it directly to the battery. No click. I opened it up and saw that the little white plunger was not all the way through the little rubber gasket to block the fuel, so it was stuck in the open position. I got the manual I ordered for it in the mail this morning, and it doesn't talk about how to repair that part, so I just got a new one.

    I put the new primer on in about 10 minutes, pulled it out into the driveway, lowered the motor into the water trough, and it fired right up and ran like a champ. I even took it to the lake tonight and caught some nice crappie and white bass.

    Now I notice that it doesn't want to idle well. It runs great with the fast idle lever up, but when I put it all the way down to go into gear, it wants to idle so low that it ultimately dies.