Logo
Get instant online access to repair manuals for your Mercury / Mariner outboard. Online Manuals
MercuryMariner
Order printed Mercury / Mariner service manuals — shipped to your door! Printed Manuals
MercuryMariner
Use engine diagrams to find & order parts for your Mercury / Mariner engine. Engine Diagrams
MercuryMariner
Find parts quickly with Mercury application guides. Quick Parts Guide
MercurySierraCDI
Results 1 to 6 of 6
  1. #1

    Default Mercury 15hp 2 stroke is misfiring

    Colleagues,

    I am troubleshooting a 2005 15 hp 2 stroke mercury that is misfiring . Once it warms up , after 3 minutes +/- , once every minute o more i get a misfire. Also noticed that is still there at higher rpms . I have been using the motor for few years and was not running smooth at idle so decided to do a carb cleaning .
    I have cleaned the carb and was fine, did not notice any dirty . Checked the sparks and seemed fine. Strong blue/white. The only thing that I did not check was compression , since did not have the compression meter.
    Any feedback from more experience people?
    cheers,

    martin

  2. #2
    Join Date
    May 2007
    Posts
    9,221

    Default Re: Mercury 15hp 2 stroke is misfiring

    Try running it at night, in the dark with the (hood) off.

    As the coils get older they develop spider web like cracks in the cases. Tough to see under all the gunk that usually ends up on them.

    If the coils are the problem you will see the "arc" when the motor misfires (also hear a sharp snap noise).

    This may not be your issue, but it's quite common - have seen it myself quite a number of times so worth checking. They will test fine otherwise because it's a "leak" not a broken winding.
    Graham

    A "professional" is someone who gets paid for their work - it doesn't necessarily mean they are good at it :)

  3. #3

    Default Re: Mercury 15hp 2 stroke is misfiring

    Quote Originally Posted by galamb View Post
    Try running it at night, in the dark with the (hood) off.

    As the coils get older they develop spider web like cracks in the cases. Tough to see under all the gunk that usually ends up on them.

    If the coils are the problem you will see the "arc" when the motor misfires (also hear a sharp snap noise).

    This may not be your issue, but it's quite common - have seen it myself quite a number of times so worth checking. They will test fine otherwise because it's a "leak" not a broken winding.
    Will give a try and let you know the results. Thank you

  4. #4

    Default Re: Mercury 15hp 2 stroke is misfiring

    Quote Originally Posted by zenonmb View Post
    Will give a try and let you know the results. Thank you
    Tried but could not see any arc . BTW, got a compression tester and both cylinders seem fine, 110 psi . Need to continue troubleshooting....

  5. #5
    Join Date
    May 2007
    Posts
    9,221

    Default Re: Mercury 15hp 2 stroke is misfiring

    Ok, then - take the hood off and look for any "pooled gloopy oil".

    Check (stick your finger) "under" the flywheel and kinda swipe it around - see if there is residue there (looking for blackish, oily, thick mess).

    Also check in the (lower cowl) around the perimeter of the powerhead (this time it could be caused by a bad base gasket, carb gasket or transfer cover gasket). What you are doing is checking for a blown crank seal (upper) or other gasket - if you have a bad seal when the cylinder is trying to (compress) the gas from the crankcase into the open intake port, if you have a bad seal the air/oil/gas mix can (blow out) so not enough gets into the cylinder and it hiccups/sneezes instead of firing normally. The gas evaporates and just leaves the 2 stroke oil at/near the (site) of the leak.

    That would be next on my list of "what to check".
    Graham

    A "professional" is someone who gets paid for their work - it doesn't necessarily mean they are good at it :)

  6. #6

    Default Re: Mercury 15hp 2 stroke is misfiring

    Quote Originally Posted by galamb View Post
    Ok, then - take the hood off and look for any "pooled gloopy oil".

    Check (stick your finger) "under" the flywheel and kinda swipe it around - see if there is residue there (looking for blackish, oily, thick mess).

    Also check in the (lower cowl) around the perimeter of the powerhead (this time it could be caused by a bad base gasket, carb gasket or transfer cover gasket). What you are doing is checking for a blown crank seal (upper) or other gasket - if you have a bad seal when the cylinder is trying to (compress) the gas from the crankcase into the open intake port, if you have a bad seal the air/oil/gas mix can (blow out) so not enough gets into the cylinder and it hiccups/sneezes instead of firing normally. The gas evaporates and just leaves the 2 stroke oil at/near the (site) of the leak.

    That would be next on my list of "what to check".
    I am traveling now and will check this when back home . What I did noticed, before seen your message, is that when put the fingers in the exhaust, the two little holes in the back, one of them the pressure is really low . So was wondering if this two holes, they are dedicated to each cylinder .

Similar Threads

  1. Mercury 15hp. 2 stroke.
    By Marela65 in forum Mercury Mariner Outboard Forum
    Replies: 0
    Last Post: 06-18-2017, 07:05 PM
  2. questions about 15hp mercury 4 stroke
    By bassnutz in forum Mercury Mariner Outboard Forum
    Replies: 4
    Last Post: 06-03-2015, 09:59 PM
  3. Mercury 15hp 4 stroke .. is it enough !!
    By mark groves in forum Mercury Mariner Outboard Forum
    Replies: 4
    Last Post: 01-09-2013, 01:39 PM
  4. Mercury 15hp 4 stroke questions
    By ZBat910 in forum Mercury Mariner Outboard Forum
    Replies: 3
    Last Post: 05-08-2012, 09:07 PM
  5. 1990 15hp mercury 2 stroke
    By ken_pike in forum Mercury Mariner Outboard Archive
    Replies: 11
    Last Post: 11-24-2008, 12:42 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •