40 hp mercury, cranking problem

Discussion in 'Bubba's Outboards' started by wylie catter, Jan 1, 2008.

  1. wylie catter

    wylie catter New Member

    Messages:
    675
    State:
    South Carolina
    I have a 93 40hp mercury, 4 cyl 2 stroke. It was recently rebuilt but the carbs weren't. It is the hardest motor I've ever tried to crank. I have to choke it while turning it over and sometimes put it in neutral giving it gas before it will hit. If its hot and only been shut off a few minutes it will start right up. Otherwise I have to go through the whole deal all over.

    I took one of the carbs off last week. It looked clean except for what looked like a little tarnish looking spot in the needle seat. I tried to get that out.

    The rubber tip on the needle also had a pretty bad impression from the seat. A freind told me if the rubber tips have a impressions I should replace them.

    I think I'm gonna order complete kits for both carbs and start fresh. I just wanted to run this by yall incase you had any other better advice.

    I've rebuilt carbs before, but never on a mercury. Is there anything special I need to know?

    Thanks.
     
  2. tspergin

    tspergin New Member

    Messages:
    867
    State:
    newark ohio
    If possible lay out all parts in order of dissasembly and take pics as you go for reference,a good manual is the best investment you can make
     

  3. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    Tony made a good suggestion on this. Those carbs do need soaking good and cleaning. You need to replace all the gaskets and needle and seats. If you will e--mail me a pix of one of the carbs I'll send you the exploded view of it and the settings you will need to do. When you tear the carbs down do it one at a time and repace them back over the same port. They need to be soaked and air blown thru all the little holes and a small wire ran thru the jets to make sure they have nothing in them at all. I do this and also I will take a can of cheap break cleaner and use the little starw that comes with the can to squirt thru the orrfices.
    Coofficer@blomand.net
     
  4. wylie catter

    wylie catter New Member

    Messages:
    675
    State:
    South Carolina
    One more question. I finally got all my parts in, and put the carbs back together last night. There is a screw near the top, it looks like an air fuel mixture screw. It has a pointed end and a spring on it.

    One was adjusted at 1 1/2 turns out from the bottom.
    One was adjusted at 3/4 turns out from the bottom.

    I put them both back at 1 1/2 turns from the bottom. Is this right?
    Do you rekon that might of been a big part of my problem the whole time?
    That lower carb was probably starving for gas.

    Thanks,
     
  5. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    That could have been your problem. I have the proper way to set those screws so I will find it and post it on here for you.
     
  6. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    Idle Adjustment
    1. The motor needs to be installed on the boat and in the water
    2. Start with the idle needle 1 turn open
    3. Warm the engine up good.
    4. With the engine running at idle speed while in forward gear turn the low speed mixture screw counterclockwise until the affected starts to load up, Or fires unevenly due to over rich mixture.
    5. Slowly turn needle clockwise until cylinders fire evenly and engine picks up speed.
    6. Continue turning clockwise until too lean a mixture is obtained and engine slows down and misfires.
    7. Set adjustment screw 1/2 to 3/4 turn counterclockwise from lean out position to gain approximate true setting.
    8. Do not adjust leaner than necessary to attain reasonable smooth idleing.
    9. When in doubt, it is preferable to have mixture set slightly rich rather then too lean.
    10. If engine hesitates during acceleration after adjusting idle, it is to lean. and idle mixture screw should be enriched slightly until engine accelerates correctly.
    11. Idle and adjust the idle stop screw on stop bracket so the engine idles at the correct speed in gear.
    12. Run engine in forward gear at WOT to clear the cylinders out and then recheck the idle speed.
     
  7. fishnohio

    fishnohio New Member

    Messages:
    58
    State:
    Middletown,Ohio
    i just want to say that Willard is one of the best advise givers on here that man seems to know everything about a boat, so big props to you Sir.....Mike
     
  8. wylie catter

    wylie catter New Member

    Messages:
    675
    State:
    South Carolina
    Thank you very very much. You're an incredible help, and a huge asset to the BOC.
     
  9. wylie catter

    wylie catter New Member

    Messages:
    675
    State:
    South Carolina
    I put the boat in the water today. It idles a little to low but that's easy to fix. It still doesn't crank good. I have to choke it some and give it some throttle in neutral when it starts to crank. If I let it run around 2000rpm for a few seconds once it's crunk, then it's good to go.

    When I was on the water I thought once I idled it up more that might fix it. But when I got home I pulled the cover off the motor and the bottom carb was leaking gas. It's a steady drip. About 1 per second. It's dripping off of the little shaft with the spring on it that runs through the housing and holds the butterfly flap thing, near where the carb bolts to the block.

    By doing this I guess it's draining the bowls somewhat. I watched it about 15 minutes and it leaked a 3" puddle of gas in my shop floor. I unhooked the fuel line and that didn't slow it down. I unhooked the gas line from the choke incase that was bleeding by or something and that didn't help. The needles are new in carbs but they're a diferent style than the old ones. The old ones were a solid needle with the tiny metal clip holding them to the float. The new ones have a little spring on the end with no type of clip.

    I was thinking I should take the carb apart and bend the float up a little to put more pressure on the needle. But I don't know, that's why I'm asking.

    By the way the adusting derections you gave me before worked perfectly on the air fuel screws. Thanks...
     
  10. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    Terry look on those carb and see if you can find some numbers or a set of letters and post them for me.
     
  11. psychomekanik

    psychomekanik New Member

    Messages:
    2,534
    State:
    Illinois
    I have a 97 merc. 40 h.p. 2 cylinder. i have the same problem. I'm guessing you have wm-4 or wm-2 carbs?? i'v rebuilt the carbs. and done every thing imagineable. one thing that did help i adjusted the float level a little so the bowls dont hold as much. My engine runs great, and i have no problems except for the leak. i gave up on it. the only time it leaks is when it's propped up. I usually unhook the gas line at the ramp, and let it run for a minute or so to lower the fuel levels in the bowls. dont run it dry! it'll lean it out too much and possibly do some damage. if you figure it out post something on it or p.m. me. i'd like to see what i missed.
     
  12. wylie catter

    wylie catter New Member

    Messages:
    675
    State:
    South Carolina
    The motor serial # is OD204971

    On top of the carb it says 7-3B 1982


    On the side plate that the fuel line hooks to it says 14494

    On the other side I didn't see much just a few letters, it was 1B WMA

    Thanks a lot Willard.
     
  13. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    That 1B WMA was what I am looking for. Is the carb leaking while the motor is in the down position or up position.
     
  14. wylie catter

    wylie catter New Member

    Messages:
    675
    State:
    South Carolina
    In the level position and the just below level position. It's on a pontoon so I never trim it up much.
    Just about 20 minutes ago I went out there and it wasn't leaking. You know yesterday I unhooked the gas and all. So I did trim it way up just for the heck of it and it started leaking again.
     
  15. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    Sounds like a warped bowl or pinched gasket between the top plate and the bowl that the float sets in.
     
  16. wylie catter

    wylie catter New Member

    Messages:
    675
    State:
    South Carolina
    Alright, I'll take the bottom carb back off and check the gasket and everything.

    Do you think I should bend the float a little so that not as much gas is in the bowl?

    Thanks.
     
  17. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    Just set it like its suppose to be or it will have a lean condition.
     
  18. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
  19. wylie catter

    wylie catter New Member

    Messages:
    675
    State:
    South Carolina
    Yep that't it. And the gas is dripping off of the #25 shaft. Where the shaft sticks out of the bottom of the carb and has the spring on it.