Posted by
Message
cgrand
New Orleans Pelicans Fan
HAMMOND
Member since Oct 2009
10787 posts
 Online 

help me diagnose a merc 25 2 stroke issue?
this is an older (late 80's) carb'd 2 stroke

all the mercury service places are weeks behind, so i'm gonna try to fix this myself. they arent that hard to work on so i'm looking for advise

while running, it will drop off to half power, and stay that way until randomly coming back up, then run a while and drop back off again. i suspect it may be electrical because if you pull the cowling you can hear a ticking noise back by the plugs, and if you touch it it will shock the piss out of you

any thoughts?


cajuncarguy
LSU Fan
On the road...Again!
Member since Jun 2013
794 posts

re: help me diagnose a merc 25 2 stroke issue?
Coil packs?


REB BEER
Laffy yet
Member since Dec 2010
9015 posts

re: help me diagnose a merc 25 2 stroke issue?
Is that a 2 cylinder? 1 of the spark plug wires may be shorting out on the head. Check wires for cracks and tape up where the wire meets the cap. My mudmotor was doing the same thing and once I taped up the plug wires 6 years ago, it hasn't done it since.
This post was edited on 8/22 at 11:24 am


Replies (0)
Replies (0)
00
keakar
Member since Jan 2017
1957 posts
 Online 

re: help me diagnose a merc 25 2 stroke issue?
your plug wire has a break and its firing to the block rather then through the plug. run it at night or with some sort of a cover to make things dark and let you get under there with it and watch to see which one it is but if its shocking you then you should already know which one it is.

if its the wire then wrap the shite out of it with electrical tape if its not the type you can replace the wires on, if its the end cap, those can be replaced. if you are very lucky and its near the end you can snip the wire shorter and reconnect the cap without needing to do anything else.

if all else fails, just pull off the flywheel and replace the whole coil and wire assembly but if you do this, dont be a goober and do it right and replace both of them, not just the one thats bad
This post was edited on 8/22 at 10:58 am


cgrand
New Orleans Pelicans Fan
HAMMOND
Member since Oct 2009
10787 posts
 Online 

re: help me diagnose a merc 25 2 stroke issue?
quote:

if all else fails, just pull off the flywheel and replace the whole coil and wire assembly but if you do this, dont be a goober and do it right and replace both of them, not just the one thats bad

thats what i was think i'd do anyway
all that shite is 25 years old now

i cannot guarantee non-goobering though

thanks guys


Replies (0)
Replies (0)
40
HeadBusta4LSU
LSU Fan
Baton Rouge
Member since Aug 2007
10940 posts

re: help me diagnose a merc 25 2 stroke issue?
Stator?


Replies (0)
Replies (0)
00
auggie
Auburn Fan
Opelika, Alabama
Member since Aug 2013
6985 posts

re: help me diagnose a merc 25 2 stroke issue?
quote:

Coil packs?


That's what I think,but I have never owned a Mercury.
Had an 80s Evinrude that acted that exact same way,and that was the problem.


Replies (0)
Replies (0)
00
Marlbud
Member since Jun 2017
144 posts

re: help me diagnose a merc 25 2 stroke issue?
It's most likely this. If not, it's the high speed jet in the carb.


Replies (0)
Replies (0)
00
Marlo Stanfield
Houston Astros Fan
Member since Aug 2008
967 posts

re: help me diagnose a merc 25 2 stroke issue?
Had an early 90s Mariner 25 in high school. Mine did that for a while and then eventually it ran on 1 cylinder only for a little while. Turned out to be the power pack.
This post was edited on 8/22 at 8:18 pm


Replies (0)
Replies (0)
00
Wtodd
Missouri Fan
Tampa, FL
Member since Oct 2013
26795 posts

re: help me diagnose a merc 25 2 stroke issue?
quote:

if you touch it it will shock the piss out of you

any thoughts?

Yes.....problem found


cgrand
New Orleans Pelicans Fan
HAMMOND
Member since Oct 2009
10787 posts
 Online 

re: help me diagnose a merc 25 2 stroke issue?
it was a bad plug...
at night you could see it sparking around the socket where it threads into the block

they were new plugs too
guess it should have checked the easiest thing first

anyway, fixed

as usual, 99% of outboard issues are either fuel or spark plug related


DownshiftAndFloorIt
LSU Fan
Here
Member since Jan 2011
48940 posts

re: help me diagnose a merc 25 2 stroke issue?
Did it look like there was a midget welding class happening under the cowling?



cgrand
New Orleans Pelicans Fan
HAMMOND
Member since Oct 2009
10787 posts
 Online 

re: help me diagnose a merc 25 2 stroke issue?
even though i could hear it ticking, and i knew it would shock me, and i could see it arc-ing...i still managed to shock myself


Replies (0)
Replies (0)
00
first pageprev pagePage 1 of 1next pagelast page
refresh

Back to top

logoFollow TigerDroppings for LSU Football News
Follow us on Twitter, Facebook and Instagram to get the latest updates on LSU Football and Recruiting.

FacebookTwitterInstagram