Bogging Problem? (35hp Mercury)

Discussion in 'Bubba's Outboards' started by Raven Blayde, Oct 23, 2009.

  1. Raven Blayde

    Raven Blayde New Member

    Messages:
    320
    State:
    Kentucky
    I bought a 1968' 35hp Mercury outboard motor back in the early part of the summer. The guy I bought it from knew nothing about the motor (other than it had been worked on by a boat motor repair shop before he got it) and had never been fired up since. He gave me such a deal on it, I couldn't pass it up. I brought it home, did a bit of cleaning and had it up and running in a couple of hours. I put the motor on my 14ft fiberglass John boat and headed to the river with it. The motor starts right up and runs great out of the water. In the water, it doesn't get any RPM's in gear. I tried adjusting the throttle linkage several times, cause I thought there might be a problem there, but it's not. In the water, full throttle only makes the boat go as fast as 1/4 throttle should be. It's not the prop slipping, or else the RPM's would be going through the roof (which it's not). The RPM's just don't go up like they should. Out of the water, I can put the motor in gear and it will redline. ?????? I tried putting brand new sparkplugs in it cause they did look a bit damp after running it, but that didn't help. I took the carb off to clean it, but to my suprise, the carb was so clean inside, you could eat out of it. I drained and relubed the lower unit to make sure everything was spinning freely, so no problem there. My next step is the points or the timing (I'm guessing). I can't think of anything else to try on this thing. I've never messed with points or timing on a boat motor, so I'll have no clue on what I'm doing here. Any advice would be greatly appreciated. Thanks in advance.
     
  2. Just_a_feller

    Just_a_feller New Member

    Messages:
    22
    State:
    Georgia
    check the flywheel key, and check the compression..sounds like you have a low compression problem..this usually is the problem when you loose power under load. Hope it helps, RC
     

  3. Just_a_feller

    Just_a_feller New Member

    Messages:
    22
    State:
    Georgia
    check both cylinders to see if both are fireing, It may be running on one cylinder. Runs good without a load but no power when you load the engine. these are just some things I have run across.
    RC
     
  4. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    Need to adjust carbs with the engine in the water =in gear- under a load

    warm the engine up before you start your adjustments.

    Start with all needles one turn open to adjust the engine to about 600 to 700 rpms

    With the engine running in gear set the low speed mixture needle counter clockwise until affected cylinders start to load up
    or fire unevenly due to an over rich mixture.

    Slowly turn the needle clockwise until cylinders fire evenly and engine picks up speed.
    continus turningclockwise until to lean of a mixture is abtained and engine slows down and misfires.

    set needle 1/2 to 3/4 turn counter clockwise from lean out position to gain a good setting
    Do not adjust any lower to attain reasonably smooth idling.

    when in doube it is better to have the mixture set slightly rich rather then lean.

    If enginehesitates during acceleration after adjustment, it is to lean and it should be enriched until acclerates properly

    Idle engine and adjust idle stop screw on stop bracket until engine operates at the proper RPM in forward gear.

    That would be about 1200 out of gear and about 600 to 700 ingear.
    After adjustments you need to run it at wot to clear it out and then recheck you idle speed.


    Hope this helps. Its easier for me to do then to write it out.
     
  5. tofish

    tofish New Member

    Messages:
    3,923
    State:
    arizona
    do this with two people in boat, or like i've had to do. parked in a mooring spot and then in gear. hey, it works that way.
    gary
     
  6. Iowa_Josh

    Iowa_Josh New Member

    Messages:
    1,463
    State:
    Central Iowa
    New carb gaskets, they say to replace them every time you take the carb apart. New hoses and clamps on every connection. If it can suck air along with the gas, it will prefer to suck air. Pump up the primer bulb and make sure there aren't any leaky connections or connectors. Make sure the bulb isn't going flat when you're running. Check the vent on the tank. Make sure the stator advances to it's full travel when you twist the grip. Sometimes a wire or something gets in the way and you can't move it the whole way. Make sure the proper gasket is around the high speed jet if there is one. You can put a clear piece if hose in the fuel system and look for bubbles(air leaks). I think you're supposed to swap out the hose afterwards for some reason.
     
  7. Tim70

    Tim70 New Member

    Messages:
    48
    State:
    Maplewood, Missouri
    I agree with RC. It sure sounds like you are running on one cylinder. You should definitely check compression. I don't know if you have an Auto Zone down there or not but you can rent a tester for free from them if you don't have one. Also look for signs of water in the cylinder to rule out a blown head gasket. Check the plugs when you pull them and see if there are any bubbles on them. Also shine a light in the cylinders and look for the same. If you find water a new head gasket is in order. Not the end of the world. Pretty easy fix really.
     
  8. catwhisper

    catwhisper New Member

    Messages:
    456
    State:
    georgia
    when you put this motor on this boat did you adjust the cavitation plate with the bottom of the boat. i think most factory recommendations are 1/2 in below the bottom of the boat. i run mine 1/2 in above seems like i get a little more speed. just a thought. these other guys are much more experienced than me. i'm a shadetree!:big_smile:
     
  9. Raven Blayde

    Raven Blayde New Member

    Messages:
    320
    State:
    Kentucky
    HA!!! Problem found!!! For those who thought it was running on one cylinder, you were correct!!! I have one sparkplug that is not getting any fire at all. I know the plug is good (It's brand new), but its not firing. The other plug is working fine. The plug that works has the normal "Camel Tan" color, but the plug thats not firing still looks as silver and shiny as the day I took it out of the box and installed it (in other words, it's never fired yet).
     
  10. Iowa_Josh

    Iowa_Josh New Member

    Messages:
    1,463
    State:
    Central Iowa
    Is there compression on that cylinder?
     
  11. Tim70

    Tim70 New Member

    Messages:
    48
    State:
    Maplewood, Missouri
    Are you getting any spark at all on that cylinder?
     
  12. Raven Blayde

    Raven Blayde New Member

    Messages:
    320
    State:
    Kentucky
    Haven't checked the compression yet (started raining on me while I was messing with it yesterday). From what I'm seeing, the plug is getting no fire to it whatsoever. The sparkplug smells like fuel also (meaning it's not firing). I can also see that someone has replaced the sparkplug wires on this motor before I bought it, because they look new. The guy I got this motor from claims it had been to a repair shop and had work done to it, but he didn't know exactly what. He also said the pervious owner told him it had never been fired up since it came back from the repair shop, so he didn't know if it would even run or not. I'm betting that's one of the things they worked on right there. Something might not be hooked up right under the flywheel? I've never pulled the flywheel on a boat motor, so I have no idea what I'm getting into here. Am I in for a mess, or should this be pretty simple?
     
  13. Tim70

    Tim70 New Member

    Messages:
    48
    State:
    Maplewood, Missouri
    Try holding the plugs about 3/8 of an inch from the block and give it a pull and see what kinda spark you have. Try both plugs and switch them around to make sure you don't have a bad plug. If you can't get spark to jump that gap then you got to start looking at the points and condensors. I have never pulled a flywheel, but alot of guys use a cheap puller from harbor freight. Just don't use the bolts that come with it they are too soft. Go get some grade 8 hardened steel bolts and use them. Good Luck
     
  14. Raven Blayde

    Raven Blayde New Member

    Messages:
    320
    State:
    Kentucky
    New findings- No bad sparkplug here. Tried another plug and still no fire. So, I pulled the flywheel to give it a look. I have no idea what I'm looking at, but I did see some things that can't be good. There are two big round black plastic parts under there that the sparkplug wires run off of. The one plastic part that goes with plug that fires looks fine from what I can see. The other one (the one that's not firing) is cracked up pretty bad. Also, there are 3 small wires that connect together from this big plastic part. At first glance, I thought they were burnt off, but after taking them off, I can see that they are not burnt, but corroded real bad. I think this might be our problem. What do you guys think?
     
  15. Tim70

    Tim70 New Member

    Messages:
    48
    State:
    Maplewood, Missouri
    That is it, bad coil. After you replace them, make sure you torque the flywheel back down to the right specs. I don't know what the recommended torque is on Mercs, but you should be able to find out somewhere. Some say if you don't torque them down right you can shear the flywheel key. By the way you can rent a torque wrench from Auto Zone as well if you don't have one.
     
  16. Raven Blayde

    Raven Blayde New Member

    Messages:
    320
    State:
    Kentucky
    Have the torque wrench covered (I've got one out here in my garage from building racecar engines). Thanks again man!!
     
  17. Raven Blayde

    Raven Blayde New Member

    Messages:
    320
    State:
    Kentucky
    I'm afraid we are back to square one again. I replaced the coil last night and fired the motor up- Still no spark coming from that plug. Tried 2 other sparkplugs- Nothing. BUT, I can hook my test light up to the sparkplug wire and it's lighting up (Pulsing like it should). It's obviously getting enough fire through the plug wire to show up on a test light, but it won't fire a plug to save it's life. Even tried putting a new sparkplug on the wire, grounding it and firing it without the plug ever being installed in the motor (in case there was something in the cylinder that could be fowling the plugs out). Still no fire from the plug. I CAN however touch the test light to the end of the sparkplug while its running and again, it lights the test light up, just no visable spark at all from the sparkplug. I'm confused as heck here and still running on one cylinder.
     
  18. Raven Blayde

    Raven Blayde New Member

    Messages:
    320
    State:
    Kentucky
    More new findings today. Took it all apart again and tried swapping what I believe to be the condensors (two small round parts on the top that are shaped like pop cans) lol.. No difference. Same plug not firing. So, I took the thing apart again and just stood there looking at the stupid thing to try to get some ideas on what to do next. I started looking at these two large "U" shaped parts on the top that I believe to be magnetic or something. Whatever these are, they are made in layers kinda like the leafsprings of a car I guess and located behind the coils. The side that is firing had worn areas on both sides of the "U" shape, as if it contacts with the flywheel. The side that isn't firing only has worn places on one side of the "U" shaped part and looks as if it's never contacted the flywheel ever. Is this a part that needs adjusted, and if so, how do I do it?
     
  19. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    Those have to have an air gap but the best I can remember you set them even with the boss that they are bolted to thart points toward the inner part of the fly wheel


    Post a picture of it looking straight down on the parts you are talking about.
     
  20. coach

    coach New Member

    Messages:
    1,564
    State:
    Greenville , Ms
    could his problem be that he just needs to sandpaper rub the u shaped part that is not firing???? it could still be picking up enough fire to lite a test light but not enough to fire a plug .................i've had lawn mowers do the same thing ................ just a thought....:crazy: