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  1. #51
    Join Date
    Apr 2005
    Location
    Bromley,Kent
    Posts
    2,807

    Default Re: Two-stroke conundrum

    Quote Originally Posted by Rum Run View Post
    The cheapo gauge I bought said 100psi with the engine spun by a drill
    I recall experiencing something similar a very long time ago, so my memory not being what it was may confuse rather than resolve but I recall that after several attempts I realised that the float control fork had been installed incorrectly(inverted I think) and correcting my error solved the problem

  2. #52
    Join Date
    Jul 2002
    Location
    Home: Kent. Boat: Chichester
    Posts
    43,614

    Default Re: Two-stroke conundrum

    Quote Originally Posted by Gin View Post
    I recall experiencing something similar a very long time ago, so my memory not being what it was may confuse rather than resolve but I recall that after several attempts I realised that the float control fork had been installed incorrectly(inverted I think) and correcting my error solved the problem
    I think there is a possibility that the trouble is something like this.

    We know the ignition is good and we know that the plug is new.
    We know the compression is reasonable
    We know fuel is getting through because the plug is getting wet ( hopefully with petrol!) but it wont run although it fires briefly with starting fluid.

    Perhaps it is not running because it is flooding,
    Therefore
    Check the assembly ,operation and setting of the float and the needle valve against the instructions in the workshop manual.

    At the same time check the operation of the throttle valve and the choke

    If you have mislaid your workshop manual one of these may cover it. I dont think you have told us what age it is

    http://www.boatinfo.no/lib/mercury/m...9_2-40.html#/0
    http://www.boatinfo.no/lib/mercury/m...0-2000.html#/0
    http://www.boatinfo.no/lib/mercury/m...1-2005.html#/0
    Last edited by VicS; 02-09-19 at 10:07.

  3. #53
    Join Date
    Nov 2009
    Location
    Home UK Midlands / Boat Croatia
    Posts
    20,314

    Default Re: Two-stroke conundrum

    Quote Originally Posted by VicS View Post
    I think there is a possibility that the trouble is something like this.

    We know the ignition is good and we know that the plug is new.
    We know the compression is reasonable
    We know fuel is getting through because the plug is getting wet ( hopefully with petrol!) but it wont run although it fires briefly with starting fluid.

    Perhaps it is not running because it is flooding,
    Therefore
    Check the assembly ,operation and setting of the float and the needle valve against the instructions in the workshop manual.

    At the same time check the operation of the throttle valve and the choke
    I didn't read the thread again and was assuming when I posted #47 that the engine had not actually fired at all .... but if it has already fired with fuel through the air intake then the problem is the carb/fuelling and flooding due to a sticking/dirty needle valve/float sounds likely although I would normally have expected a few seconds of lumpy running before it stalls.

    Possibly try a start with the starting fluid and no choke but the throttle 1/4 open. If that produces a longer burst of firing but then a stall as soon as the throttle is closed, flooding is pretty much confirmed.

    Richard

  4. #54
    Join Date
    Apr 2011
    Location
    Me: Midlands, Boats: East Coast
    Posts
    370

    Default Re: Two-stroke conundrum

    Quote Originally Posted by dancrane View Post
    Reading this tale of frustration, I'm alarmed at the possibility that your Mariner 5hp is the same as mine (as yet untried).

    Does it look the same as mine, below?

    I'm keen to avoid ever doing what you did, which seems to have put yours to sleep. Where was the fuel leaking from?

    No, the cover is black, though aren't they all basically tohatsu M5 engines?
    I fixed a leak between the inside tank and the fuel tap and put in fresh fuel. The latter may have been the problem!
    Last edited by Rum Run; 03-09-19 at 18:29.
    De'il ding a divot auf yer wame wi a flaughter spade

  5. #55
    Join Date
    Apr 2011
    Location
    Me: Midlands, Boats: East Coast
    Posts
    370

    Default Re: Two-stroke conundrum

    The blaggard is now running, at least in the tank.
    I believe that the new fuel I bought may have been Ultimate 97 octane petrol. When running on the inside tank with boring 95 octane shopping car petrol it worked! When using the outside tank with the suspect fuel it coughed and stopped. This is all at low throttle settings as the test bin chuck water everywhere else.
    Have not tried hand starting yet, which will be tomorrow's job.
    F#<€ !!!!

    Thanks to all who made suggestions, it has helped confirm that something magical had not gone wrong.
    De'il ding a divot auf yer wame wi a flaughter spade

  6. #56
    Join Date
    Jul 2002
    Location
    Home: Kent. Boat: Chichester
    Posts
    43,614

    Default Re: Two-stroke conundrum

    Quote Originally Posted by Rum Run View Post
    The blaggard is now running, at least in the tank.
    I believe that the new fuel I bought may have been Ultimate 97 octane petrol. When running on the inside tank with boring 95 octane shopping car petrol it worked! When using the outside tank with the suspect fuel it coughed and stopped. This is all at low throttle settings as the test bin chuck water everywhere else.
    Have not tried hand starting yet, which will be tomorrow's job.
    F#<€ !!!!

    Thanks to all who made suggestions, it has helped confirm that something magical had not gone wrong.
    You sure it was not diesel ? ITYWF that would explain all the symptoms you have described.

  7. #57
    Join Date
    Nov 2009
    Location
    Home UK Midlands / Boat Croatia
    Posts
    20,314

    Default Re: Two-stroke conundrum

    Quote Originally Posted by VicS View Post
    You sure it was not diesel ? ITYWF that would explain all the symptoms you have described.
    Indeed Vic. I can't see any reason why the engine would not run on 97 octane rather than 95.

    Richard

  8. #58
    Join Date
    Dec 2010
    Posts
    8,651

    Default Re: Two-stroke conundrum

    I read somewhere (probably this forum, maybe even this thread ) that the less bio-ethanol there is in the petrol, the better a 2-stroke will run...

    ...so something like Shell's costlier higher-grade 97 is a better bet for smooth running. I can't remember the details, beyond the fact that unless you go through large quantities of fuel, the higher cost per litre isn't much to pay for smooth running.

  9. #59
    Join Date
    Apr 2011
    Location
    Me: Midlands, Boats: East Coast
    Posts
    370

    Default Re: Two-stroke conundrum

    Quote Originally Posted by VicS View Post
    You sure it was not diesel ? ITYWF that would explain all the symptoms you have described.
    Good point. Will do a flammability test on a small amount later since I cannot tell the difference by smell.
    De'il ding a divot auf yer wame wi a flaughter spade

  10. #60
    Join Date
    Dec 2010
    Posts
    8,651

    Default Re: Two-stroke conundrum

    I can't find the guidance that specifies exactly which manufacturer's two-stroke oil is favoured for use in small Mariner/Mercury engines...anybody know?

    Sorry Rum Run, again it's not much to do with your question. Hope you get it sorted.

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