15 hp Yami Issues.

Discussion in 'Outboard Maintenance' started by AfterHours2, Apr 19, 2011.

  1. AfterHours2

    AfterHours2 Stripper in my own Mind!

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    Well my new to me 2 stroke yami started running funny the other day so I decided to tear into the carbs for a cleaning. After hitting the water the motor does not want to hit high rpms at full throttle and is not very responsive. I took the cowling off and messed with the 2 plug wires and it seemed to open up after that but still seems like it can run higher rpms. Could it be a bad plug coil wire or am I missing something else. Bad fuel perhaps? Any help would be greatly appreciated. Thx!
     
  2. cutrunner

    cutrunner Cert. Yamaha technician

    Chances are your plug wire, coil, cdi, and stater will Never go bad.. Yamahas just good at electronics, unlike merc. Its either you missed something in the carb, it needs new plugs, or you messed with an adjustment. ( dont take that the wrong way as i dont know your mechanical abilitys)
     

  3. AfterHours2

    AfterHours2 Stripper in my own Mind!

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    Thx for the quick reply. Im going to try out the plugs today. I don't think it has anything to do with the carb because it is acting the same way before/after the carb clean. I could be wrong though. Thx for the info.
     
  4. cutrunner

    cutrunner Cert. Yamaha technician

    Make sure to use the ngk plug it calls for. Dont cross refrence to a champion or anything else
     
  5. AfterHours2

    AfterHours2 Stripper in my own Mind!

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  6. AfterHours2

    AfterHours2 Stripper in my own Mind!

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    Well after a quick plug change and some fresh gas the motor is still doing the same thing. Its odd because it only happens when you put a load on the motor. Ive pretty much done all the basic fixes to the motor and now Im scratching my head on this one. Could it possibly be something in the lower unit. When you hammer the throttle down it is very sluggish and eventually picks up speed later on for a little while then slugs back down. Any other opinions please.... :(
     
  7. Brett

    Brett > PRO STAFF <

    Have you tried running it after dark with the cover off?
    One of the easiest ways I know to find arcing circuits
    that aren't visible to the eye during daylight hours.
    Anything that interferes with your ignition will slow you down.
     
  8. bsdbum

    bsdbum I Love microskiff.com!

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    I have been helping some (not much) trying to get this motor running right.  I can add that we did a full carb break down but did not adjust any needle's or HS / LS screws.  I have been thinking it seems like it could be a carb adjustment issue from the low speed to the high speed circuit.  When we rev the motor it seems to run strong and turns high RPMS up to the rev limiter.  The problem shows up when the motor is under load.  Could it be a hi speed screw that needs to be opened up? 

    If someone could give me a good starting point for what the screws should be at that would be helpful.  Also we did a compression test and 130/130 each hole.  Plugs look a little white we are running 50-1 fuel ratio.

    :eek:


    Thanks for the help!!
     
  9. floridanative1028

    floridanative1028 I Love microskiff.com!

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    I'm not %100 positive but I think that engine is supposed to run on a 100:1 mix.
     
  10. cutrunner

    cutrunner Cert. Yamaha technician

    Whatever you do , DO NOT adjust any of the screws. I hate to say it but you must have missed something in the carb, its not hard to do in those little motors, especially japanese. Heres how you find out what it is, and please try it before tearing into unnessecary things. Running the motor on land will not show you anything. It must be run under a load in the water. So, take the boat to the ramp. Take off the hood, and then take off the the plastic intake cover that goes over the carb. Now comes the trick part. Start getting it on plane to the time where it starts running weird then carefully cover half to 3/4 of the carb with your hand(as in your trying to cover the carb throat) all your doing is choking the motor. If it bogs even worse its not the carb, if it picks up it is your carb. I it seems to run perfect and idle perfect on the hose then bog at mid/ throttle under load its got to be a mid range curcuit or the high speed jets clogged. Thats it. Like i said the small motor carbs have very small jets and passages. Im really not trying to tell you , that you didnt do a good enough carb job, just merely helping you as i am a yamaha tech for a living
     
  11. AfterHours2

    AfterHours2 Stripper in my own Mind!

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    Thx cut runner and brett for the help. Once Im home today I will try everything mentioned and hopefully come to a final verdict. I just want my speed back... :mad:
     
  12. firecat1981

    firecat1981 BBA Counselor

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    I was just skimming over this topic and I may have missed it, but what RPM's does your tach say you are running? If you don't have a tach then you won't know where you are.

    I have a 20hp yamaha 4-stroke. When I bought it, after breaking it in, I swore it was only at like 3500 rpm's at WOT on the water and convinced I needed a different prop or it wasn't tuned right ot something. I bought a tiny tach and it turned out the motor was at like 5500 rpm's, exactly where it should be. It just sounded so different running under load then it did sitting static.

    Basically I'm saying there might not be anything wrong, But you won't know until you check the RPm's. I don't know what boat you are pushing with it, but remember it's a small motor and won't be a speed deamon.
     
  13. AfterHours2

    AfterHours2 Stripper in my own Mind!

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    When I re prop the motor I probably will get a tiny tach and put it on there. I wish there wasn't anything wrong with it and it was just me but thats just a dream. The motor is on a highsider and should push it along nicely. Just got to get home and break out the drawing board again.
     
  14. AfterHours2

    AfterHours2 Stripper in my own Mind!

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    One word "SeaFoam". I ran a whole pint in my 3 gal. and it not only cleared the jet that was clogged but also made the throttle more responsive than ever. Best $10 I ever spent... :)
     
  15. firecat1981

    firecat1981 BBA Counselor

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    Good deal, I always! run an additive in my boat tank, keeps things running nice. Usually Startron, but seafoam will work too. ;)
     
  16. AfterHours2

    AfterHours2 Stripper in my own Mind!

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    Well after a few runs the motor seems to be doing the same thing. I bought a rebuild kit, installed and cleaned the carb and jets today and took it out. The motor actually ran worse. Im just running in circles as to what this motor might need. Could it possibly be a problem with the lower unit? It runs fine on the ear muffs in the driveway but only acts up when it is put under a load in the water. This thing is driving me crazy and any help would be appreciated. Thx
     
  17. Brett

    Brett > PRO STAFF <

    When an outboard acts up, it can be the most frustrating thing to deal with.
    But the rules are simple...Air, fuel, spark, timing, compression, cooling, lubrication.
    Any of the items listed above can affect how your outboard runs.

    My outboards are carbed and my trouble shooting routine is this:

    Check the kill switch...make sure it's not activated.
    Verify the vent is open on the tank.
    Quick visual check for spark at plugs, condition of plug tips. Clean if covered in crud.
    Drain fuel tank, check for contamination by dirt or water.
    Verify interior of fuel tank is clean, including pickup screen.
    Air leaks between the tank and pump have to be eliminated.
    That means every fitting from pickup tube to the fuel pump has to be inspected and tested.
    Brittle or cracking fuel hose and primer bulb means time to replace.
    O-rings in connectors may need replacing.
    Verify hose integrity from connector to fuel pump, including last-chance filter.
    Clean or replace fuel filters, check water separator.
    Pressure test fuel pump to verify function.
    Verify hose integrity between pump and carb.
    Hoses under the cowl are exposed to heat-vibration and get brittle. Replace if needed.
    Check intake vacuum pressure.
    Check integrity of scavenger tube from crankcase.
    A cracked or broken tube changes the fuel/air ratio.
    Rebuild carb, verify every passage is clean and clear.
    Sometimes bits of metal from the machining process make it into the carb.
    Solvents won't remove those bits from the idle passageways.
    A manual/visual inspection has to be done to ensure a true and complete cleaning has been done.
    Replace the carb float, don't keep using the old one, they do leak and lose buoyancy.
    Replace float valve and valve seat, vibrations will change the shape of the tip and seat, they won't seal properly.
    After reassembling carb and installing, check linkages and throttle sychronization.
    Verify choke settings and idle settings.
    Run compression test.
    Replace spark plugs, one of the easiest things to do to make an outboard run better.
    Plugs don't last forever, recommended replacement is after 300 hours of use or 3 years, max.
    Replace spark plug wires at 5 years due to resistance build up and cracking of insulation.
    Run outboard at night with cowl off, check for visible sparks, including from under flywheel.
    Check spark with a spark gap tester, easy to buy or make one.
    Obtain a volt-ohm meter and learn to use it.
    Use the meter to test the ignition components, specs are in the OEM manual.
    Coils, CDI controllers, sensors, stators have specific resistance readings at each wire connection.
    if readings are outside OEM manual parameters, replace.
    On older outboards, check ignition timing.
    Check throttle cables for fit. Any play or looseness can result in low rpms on the water.
    Ensure proper oil levels are maintained in 4 strokes, proper mix in 2 strokes.
    Check water pressure exiting block, check thermostat, poppet valve.
    Check engine overheat sensor. (again, info in OEM manual )

    Lots of steps there, but it's what I have to do sometimes
    in order to find the problem...or in some cases, problems.

                                        :'(



    New outboards have brain boxes that record engine data
    and that info can be read by a computer connection.
    I'm not looking forward to having to buy that software.
     
  18. twitch

    twitch Well-Known Member

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    Did you soak the carbs in carb dip or just spray the passages with carb cleaner?

    Soaking them over night in the dip works much better than a couple of squirts of carb cleaner in a can.
     
  19. firecat1981

    firecat1981 BBA Counselor

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    Just curious, do you have a water seperator installed?
     
  20. flyfshrmn82

    flyfshrmn82 Well-Known Member

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    I second the fuel additive comments. Also, not all two stroke oils are the same. Take it from me. I have torn my 15 yami 2stk engine apart 3 times after running 3 different oils. The oil I ran through my engine first (west marine) left a very stick film in my engine. I switched to Yamalube and ran for 50+hours then took back apart to inspect. Thin, shinny, happy and clean running little engine now.
     
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