mercury 1150 problems need help ASAP

Discussion in 'Outboards' started by Cory247, Sep 24, 2013.

  1. Cory247
    Joined: Sep 2013
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    Location: wynnum

    Cory247 Junior Member

    Hey guys so as some of you know my mercury 1150 is.getting the better of me lately I have had problem after problem but slowly but surely getting through it thanks to you guys anyways this afternoon I decided to go and buy a.compression tester and a timing light I didn't go with the cheap stuff just incase it's a little dodgy so it cost me $350 for the both of them I have just finished doing a compression test and the results are as follows from cylinder 1 to cylinder 6 in P.S.I; 140,137,125,135,140,132. Im not sure what the readings should be close to but they are all in the green zone on the compression gauge so im wondering can anyone tell by these results if there is a fault in any cylinders? Im concerned about cylinder #3 with a reading of 125 P.S.I because it seems alot lower than the rest however it was still in the green zone by 20 P.S.I also I will state that I conducted this test 3 times on each cylinder just to be sure and tge readings were exactly the same all three times as the ones stated above.
     
  2. CDK
    Joined: Aug 2007
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    Location: Adriatic sea

    CDK retired engineer

    Cyl #3 does have slightly less compression, but still more than 8:1 so nothing to worry about. The cause can be anything from a very shallow scratch in the cylinder to some air leakage in the spark plug hole during the test.
    During normal engine operation such small deviations are meaningless.
     
  3. Cory247
    Joined: Sep 2013
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    Location: wynnum

    Cory247 Junior Member

    Ok awesome so those results are passable well that's a relief, only thing is now I have no idea what is causing my engine not to start I have fuel, spark and compression and I have never fiddled with the timing although when I do get it to start I will be checking it with the timing light, have you got any.suggestions as to why an outboard will not start?
     
  4. CDK
    Joined: Aug 2007
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    Location: Adriatic sea

    CDK retired engineer

    Timing error in outboard engines can cause loss of power at higher throttle settings (late) or backfire during starting (early), but are not large enough to prevent starting.

    Basically, a combustible mixture of gasoline vapor and sufficient high voltage to generate sparks during cranking is all it takes to start.
    Because during cranking the battery voltage collapses by 20-50% it is quite possible that an ignition system showing sparks during tests doesn't fire spark plugs in a cylinder when there is 120+ psi pressure.

    A simple way to find out where the problem lies is to use a butane or propane torch. A helper can feed a small amount of gas from the torch to the intake manifold while the engine is cranked. No choke is required. If the engine starts, switch it off immediately because there no oil to lubricate it: the problem is in the fuel system.
    If it does not start, the problem is electrical.
     

  5. Cory247
    Joined: Sep 2013
    Posts: 26
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    Location: wynnum

    Cory247 Junior Member

    Ok yeah I'm following what you're saying and as you said at the start of that reply how the engine backfires while starting that the timing is early that's what mine does on the odd occasion it wants to fire every other time I will just be sitting there cranking it and nothing happens most of the time it doesn't even try and fire just turns over, this is really starting to get the better of me as I just cannot figure out why she won't start
     
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