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  1. #1

    Default Mercury 110 9.8 hp 1971-1974 2stroke won't start except for with starter fluid, won't run

    Hi all,

    Thanks for clicking on this thread.

    Do you know about 9.8 Mercury 110 2-stroke engines? Mine ((serial# 3923125 (1970-1974, i think)) will only start with starter fluid, and won't run after it burns it off. Yes, its dangerous for the motor; I am careful not to over do it with the ether. Anyway, it won't run, as if it is not getting fuel.

    Me: no experience with outboards, limited 2stroke experience past carb cleaning my chainsaw or motorcycle. Please explain like I am 5 years old if you use parts names only on outboards.

    The Motor:
    Compression: symmetrical climb to 120 exactly on both cylinders after four pulls
    spark: great on both cylinders ~1/4inch
    Spark plugs: the top cylinder spark plug is dry compared to the bottom
    Carb: took apart (twice), cleaned with carb cleaner, afraid to soak it overnight for fear of gasket distortion on difficult to find parts. It looks very clean. Pressurized carb cleaner moves freely through the jets.

    Back story:
    When purchased, the motor was sometimes hard to start and often required starter fluid to get going. It was stored improperly for two years by previous owner, who said it was "rebuilt" by his mechanic prior to that storage. The previous owner ran some West Marine fuel system cleaner treatment, and it worked well enough for me to buy it and run it ~5 times on the water.

    While in my possession:
    It sat unused for a month, so I tried to start it in the test tank to be nice to it during storage. It ran for a while, roughly, then suddenly had trouble peeing after it got warm. This is when it really started acting wrong. I cleared the exit point on housing for the water of black hard deposits and it peed normally, but began running rough and sounded different (weaker?), then stopped running. The kill switch broke (when I pushed it), but it still would start with ether. Then it would not start at all without starter fluid. A few minutes later of running, it quit.

    I became aware of the whole ethanol problem for outboard motors at this point and got new fuel and treated it.
    I pulled the carb, tested and cleaned the plugs and tested compression. It pees fine, but will not run past the ether blast.

    It will run for a second if I put gas/oil mix directly into the cylinder via spark plug hole.

    My questions:
    -Does anyone have a cross section diagram of a 2stroke outboard similar to mine I can study?
    -Is there a fuel pump? How does the fuel move to the cylinder(s) from the carb?
    -What is the seal/gasket under the pull rope that appears loose here and is it a problem?
    -Are there any carb adjustments i should try besides the idle screw on top (closed, then opened to 1.5 - 2 turns)?
    -Does anyone need a large, smelly paperweight near Austin, Texas?

    I would really like to learn this stuff for myself for safety on the water.

    Thanks again for looking and thanks in advance for any help you can provide. My wife, dogs and chicken really want to go out on the lake soon, and I am failing them all.
    Last edited by dustfish; 06-25-2012 at 02:51 PM. Reason: Omit as many instances of the word "I" as possible and add photo of crew.

  2. #2
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    Default Re: Mercury 110 9.8 hp 1971-1974 2stroke won't start except for with starter fluid, won't run

    It has to be a fuel issue...pump most likely. Follow the fuel line.
    Fix minor things (replace wear items for preventative maintenance.) that cause major problems before they break.

  3. #3

    Default Re: Mercury 110 9.8 hp 1971-1974 2stroke won't start except for with starter fluid, won't run

    Thanks for the reply.
    The fuel line goes into the carb, then how does it get into the cylinder? What draws/pushes the fuel into the cylinder? what orifices downstream of carb may be clogged? Where is the fuel pump?
    Thanks again

  4. #4
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    Default Re: Mercury 110 9.8 hp 1971-1974 2stroke won't start except for with starter fluid, won't run

    Later ones (like yours) have the fuel pump as part of the carb. If so, a pulse from the crankcase enters the pump via a hole in the carb to crankcase gasket area to operate the pump.

    Had this same thing happen to me with an older Merc 110 only yesterday. Honestly! The problem was that the float level was too high--so high no gas came in. I lowered it a bit and away she went. You might try that. Oh, and when you pull the carb, check to see if it leaks gas all the place (as it should).

    Jeff

  5. #5

    Default Re: Mercury 110 9.8 hp 1971-1974 2stroke won't start except for with starter fluid, won't run

    Thanks! I will see about adjusting the float level right now. I guess I loosen the brass seat for the spring loaded, pointed needle that moves with the float?

    Yes, the carb leaks fuel.

    Thanks again, I will report back when done.

  6. #6

    Default Re: Mercury 110 9.8 hp 1971-1974 2stroke won't start except for with starter fluid, won't run

    Quote Originally Posted by fastjeff View Post
    Later ones (like yours) have the fuel pump as part of the carb. If so, a pulse from the crankcase enters the pump via a hole in the carb to crankcase gasket area to operate the pump.

    Had this same thing happen to me with an older Merc 110 only yesterday. Honestly! The problem was that the float level was too high--so high no gas came in. I lowered it a bit and away she went. You might try that. Oh, and when you pull the carb, check to see if it leaks gas all the place (as it should).

    Jeff
    Jeff-
    I think I correctly adjusted the float by slightly bending the tab which actuates the inlet needle. No luck; I bent the tab down with respect the the carb assembled and sitting upright.
    Thank you for the suggestion.
    Last edited by dustfish; 06-25-2012 at 07:53 PM.

  7. #7

    Default Re: Mercury 110 9.8 hp 1971-1974 2stroke won't start except for with starter fluid, won't run

    Kimcrwbr1, Thanks for the seaway.com link; great schematics! Unfortunately, I do not know how to check the upper crankcase seal, but I will now try to learn. Is it referenced in this diagram? If so, what #?

    Also, is this loose looking seal/shim important?

    After putting fuel in the top hole only- it fired for a moment, after putting fuel in the bottom hole only it fired for a moment. After putting three vacuum line doses of fuel mix in both cylinders and choking it, it ran for nicely for 10 seconds or more, mostly responded to throttle control, and then died when I took off the choke.

    What do you think? Upper crankcase seal still?

    Thanks again!
    Last edited by dustfish; 06-25-2012 at 08:19 PM.

  8. #8

    Default Re: Mercury 110 9.8 hp 1971-1974 2stroke won't start except for with starter fluid, won't run

    Quote Originally Posted by kimcrwbr1 View Post
    Yours is a 1974 is the spark a bright blue snap at 1/4 inch. Try turning the idle air needle out 2/1/2 to three turns out and see if you can get the upper plug wet with fuel. The proper adjustment for the float is holding it upside down the float should be exactly 1/4 inch above the surface of the float bowl cover.
    Re: adjusting the float... You mean while holding it upside down the float should be 1/4 inch above the bowl seat/seal? If not, I am confused.

    I will go try those adjustments now.

    Thanks so much, its 104 here today, and I need some lake time.

  9. #9

    Default Re: Mercury 110 9.8 hp 1971-1974 2stroke won't start except for with starter fluid, won't run

    Quote Originally Posted by kimcrwbr1 View Post
    Yours is a 1974 is the spark a bright blue snap at 1/4 inch. Try turning the idle air needle out 2/1/2 to three turns out and see if you can get the upper plug wet with fuel. The proper adjustment for the float is holding it upside down the float should be exactly 1/4 inch above the surface of the float bowl cover.
    Okay! +100 internet points for you and Jeff; much improvement after adjusting the float and needle. Does it look right in the photo?

    It starts and runs now without ether. However, it does not have the power to spin the prop and dies if I put it in gear and add any throttle.

    I will try your suggestion about testing the cylinders while it is running now.

    Thank you Thank you

  10. #10

    Default Re: Mercury 110 9.8 hp 1971-1974 2stroke won't start except for with starter fluid, won't run

    Everything you are saying sounds correct. It loves the choke. Also, I noticed it became way harder to start and keep running when water was added to the tank to cover the exhaust ports. And it kinda stopped/slowed peeing at some points.

    I will buy some gasket maker tomorrow, surface the carb (and the engine block may have a scar to work on also), adjust the idle screw as you suggest, torque the carb as described and report back. I will also make sure the spark is bright blue at 1/4 inch as you suggested earlier.

    BTW, I have no more canine urine in me b/c the motor shocked it out of me when I tested taking out the plugs while it was running. My dumb for using my hands! It died; it must be correctly running on both cylinders...

    Thanks again and please have a good night. You are wonderful.

  11. #11

    Default Re: Mercury 110 9.8 hp 1971-1974 2stroke won't start except for with starter fluid, won't run

    No worries, a good shock now and again keeps me lively. I will try the cylinder test again.

    The plugs currently on this motor are strange. They have no hook to bend and set the gap, like typical plugs. They have flat electrodes. Is this configuration used for premium plugs? Do you think I should replace them?

    Should I use the board you describe, or can I check the spark tonight by holding the plug near the engine block?

    There will be a helper holding the plug with insulated pliers 1/4 inch from a metal engine surface, monitoring the spark while I pull the cord. Is this right?

  12. #12

    Default Re: Mercury 110 9.8 hp 1971-1974 2stroke won't start except for with starter fluid, won't run

    Ok. We just tested the spark. It seems like the bottom cylinder had a slightly whiter spark, and it was more prone to shocking me; it did jump a 1/4 inch, just not quite as easily. The board you described must be built also to make certain it was not me moving around too much while the motor was pulled.

    The motor did not run for me just now, so I was unable to pull the plug wire with it running to test if it would run on one cylinder.

    Tomorrow I will do the carb gasket and mounting work and test the ability of the motor to run on one cylinder. I plan on shooting some video to see if that helps with the diagnosis.

    Thanks again!
    Last edited by dustfish; 06-26-2012 at 12:05 AM.

  13. #13
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    Default Re: Mercury 110 9.8 hp 1971-1974 2stroke won't start except for with starter fluid, won't run

    Regular plugs can be used on these Mercury motors !

  14. #14

    Default Re: Mercury 110 9.8 hp 1971-1974 2stroke won't start except for with starter fluid, won't run

    Quote Originally Posted by kimcrwbr1 View Post
    It should run on just one cylinder I was going to tell you to pull a plug wire while it was running but make sure the pliers are well insulated. You can kake a spark gap tester with a couple plug wires and a board withwire staples ground one to the block and stick the other in the plug wire and set the gap between the wires stapled to the board. Your local part store should have one also.
    Well my motor began running great so I did not do the single cylinder test. I will keep this in mind and do it before any use on the water.

  15. #15

    Wink Re: Mercury 110 9.8 hp 1971-1974 2stroke won't start except for with starter fluid, won't run

    Hi all,

    My motor is now running great. It idles, shifts without dying, has power at high rpm and starts on the first pull!

    Solutions that worked for me:

    1) float adjustment (when carb is upside down, the float should rest 1/4 inch higher than the carb body where the bowl attaches). I had to adjust this twice. Tolerance 1/32 inch. I simply bent the tab that actuates the needle valve. Be careful not to loose the spring loaded needle valve under the float if you remove the float. I had to search in the dirt twice to find it.

    2) Rebuilding and cleaning the carb 4 times! I kept thinking it was clean, but when I rereopened it, I found more jets and black gasket pieces from the little gasket inside the bowl. Finally, I removed this and made a new one. Luckily, only 4 bolts gets the carb off of the motor.

    3) Sealing a vacuum leak where the carb attaches to the motor. (I fixed it with grey/black liquid gasket maker from a tube; the expert suggested making a gasket out of blank gasket material from the auto parts store, but I misunderstood. I guess I'll pay later, see post #15 above. I did resurface with 220 as suggested.

    4) Clearing blockage from where the water pump "pee" exits the outer motor housing. It was obstructed by deposits.

    5)Finally, proper needle valve adjustment for this motor as described in post #19 above.

    6) If this does not work for you, don't be afraid to start a new thread. I reviewed the other threads for my motor first, and they did not work for me. I registered in a moment and had help within 30 minutes. I got my motor running in 24 hours after starting this thread thanks to all the wonderful members here, especially kimcrwbar1.

    7)Maybe everyone knows this already, but seaway.com has great schematics, part numbers, etc for this motor.

    Thanks again for all your help marineengine.com members, please reply to this post if you are ever in Austin, TX and need any type of hospitality.

  16. #16
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    Default Re: Mercury 110 9.8 hp 1971-1974 2stroke won't start except for with starter fluid, won't run

    Congrats! Your Merc Tech diploma is in the mail!

    Jeff

  17. #17

    Default Re: Mercury 110 9.8 hp 1971-1974 2stroke won't start except for with starter fluid, won't run

    Having similar issues. Going to check the float height and install news seals/gaskets. My problem is when running at full throttle is dies as if it is not getting enough fuel...just before it dies I squeeze the bulb and can keep it running. Note: the bulb isn't hard when squeezing it

  18. #18
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    Default Re: Mercury 110 9.8 hp 1971-1974 2stroke won't start except for with starter fluid, won't run

    The fuel pump operates from crankcase pressure pulses.-----If pulses are weak then it can not supply enuff fuel for high speed operation.-------Test or have a technician test crankcase pressures.----The bottom crancase seals are known to go bad and engine needs to be taken apart to replace it.---Sounds like a big job but not that hard to do.--------Or maybe you can borrow another tank and fuel hose for a test run first.-Maybe pull the fuel pump apart for inspection too.

  19. #19
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    Default Re: Mercury 110 9.8 hp 1971-1974 2stroke won't start except for with starter fluid, won't run

    Rebuild the fuel pump. Bulb should not stay hard after starting it. Give it a good cleaning and blow out the fuel passages with compressed air.
    Fix minor things (replace wear items for preventative maintenance.) that cause major problems before they break.

  20. #20

    Default Re: Mercury 110 9.8 hp 1971-1974 2stroke won't start except for with starter fluid, won't run

    I thought that once the motor had been primed that it should maintain it. I know i have a possible bad gasket ring seal because when i prime it the fuel comes out of the seal. I can take a picture of the part. I think it gas is leaking during prime that air will be getting sucked in. I have taken apart the carb once already made a few gaskets and have blown the carb w air and carb cleaned.

  21. #21

    Default Re: Mercury 110 9.8 hp 1971-1974 2stroke won't start except for with starter fluid, won't run

    Quote Originally Posted by kevster47905 View Post
    I thought that once the motor had been primed that it should maintain it. I know i have a possible bad gasket ring seal because when i prime it the fuel comes out of the seal. I can take a picture of the part. I think it gas is leaking during prime that air will be getting sucked in. I have taken apart the carb once already made a few gaskets and have blown the carb w air and carb cleaned.
    Heres a quick pic of the bad ring
    http://www.flickr.com/x/t/0098009/ph...05/8517796888/

  22. #22
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    Default Re: Mercury 110 9.8 hp 1971-1974 2stroke won't start except for with starter fluid, won't run

    Simply put the bulb does NOT need to stay hard when the motor is running !!-------One of the most misunderstood things about outboard motors I would say.

  23. #23
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    Default Re: Mercury 110 9.8 hp 1971-1974 2stroke won't start except for with starter fluid, won't run

    Leaking check valves.

    Jeff

  24. #24
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    Default Re: Mercury 110 9.8 hp 1971-1974 2stroke won't start except for with starter fluid, won't run

    does anyone know what the crankcase pressure should be i think i may be having a fuel pump pulse problem. Thanks

  25. #25
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    Default Re: Mercury 110 9.8 hp 1971-1974 2stroke won't start except for with starter fluid, won't run

    Weak fuel pump. The skinny one Merc used on some of those motors was so weak, they issued a bulletin on replacing it with a Mikuni pump. I've upgraded dozens of them, often using the later Merc pump (that's much thicker).

    Jeff

  26. #26
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    Default Re: Mercury 110 9.8 hp 1971-1974 2stroke won't start except for with starter fluid, won't run

    Jeff my Merc 9.8 is an 80 or 81 do you think it could be (the thicker one) or if not is this mikuni pump a direct replacement or an additional add on apparatus ?

  27. #27
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    Default Re: Mercury 110 9.8 hp 1971-1974 2stroke won't start except for with starter fluid, won't run

    Fuel pump. These motors don't have a lot of vacuum to keep the smaller pump Merc used on them working. (Later ones have a much larger pump that works fine.)

    Merc put out a bulletin showing how to adapt a Mikuni FP to their motors!

    Jeff

  28. #28
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    Default Re: Mercury 110 9.8 hp 1971-1974 2stroke won't start except for with starter fluid, won't run

    OK thanks Jeff thanks for your reply ill look into that bulletin from Merc. I followed that thread from Dustfish and there was some good stuff there that helped me so thanks again...Boeggie

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