Mercury 25XD won't start

[Krellz14]

Alright try this one guys. a little background information first, the year is somewhere in the 84-86 range and a 25XD. just like most all these motors it idles really bad but recently it would kill when i let it idle for less than a minute without putting it in gear either forward or reverse. it started pretty easily always and this particular time took a 2 pulls and me and my buddy were off fishin. we were out driving around looking for an underwater rock pile and when we were having trouble finding it i let off and let it idle down and it killed. i couldn't get it started and still haven't been able to since. i've checked the compression both cylinders are at 110, i'm getting good spark, newly mixed gas, i'm pretty sure the carb it still good and i'm getting gas through the system, it turns over and everything sounds good but it won't fire up and run. and i know its not something you are supposed to do but we hit it with some starter fluid (ether) and that still didn't have any effect. any ideas whats wrong or anything else i should be testing

 

[grandpaclint]

Re: Mercury 25XD won't start

i can't help you with you're problem cause i have the same problem

however i am a retired small engine tech, and starter fluid is bad for small engines,,,,the best starting fluid is carb cleaner,,serves two purposes.

if any motor wont fire with carb cleaner,it is absolutely NOT a fuel problem.
offhand i would say its a reed valve problem,maybe even a flywheel key way
has sheared.

good luck

now i need to know how to start my damn 25,,,easier---lol

 

[will941s]

Re: Mercury 25XD won't start

These motors whether it's new or old shake rattle and roll at idle, and over time knocks the carb out of adjustment. More than likely you need to re-adjust it to get it going again.....do this to mine pretty often. It will slowly begin to idle like crap over time, and with 5 minutes of tuning it's back to normal.

Try this: Back it in the water and leave the boat anchored to the trailer. Start the motor and put it in gear (just in gear, give it no gas). Slowly turn the idle mixture screw (front/top of carb) clockwise (lean) by very very small incriments until it begins to run like crap and die. Then turn it counterclockwise (rich) by very very small increments until it begins to run like crap and die. Then turn it between 1/8th and 1/4 turn cockwise until it will stay at idle in gear. You want it set on the rich side of that good idle majic point.

After that, hit the gas a few times, and go through the phases (gas, neutral, idle) to make sure it will idle after you return from max rpm's. Hope this works, and 90% of the time this is the problem. If it don't help, rebuild and clean the carb and try the process again. Keep us posted.

 

[Krellz14]

Re: Mercury 25XD won't start

OK well i did get it started finally it was not the reed valves i did check those the problem i believe is indeed in the carb and will try what will941s suggested. as i was out trying different things to get it started i put it in gear because when i use to start it i'd have to put it in gear usually pretty quickly to get it started. i held back the stop that prevents you from starting it in gear pulled and she fired right up i let it run a little and burn off some of the gas in there. i then put in in neutral and it started and ran fine. i believe that adjusting the idle mixture screw should do the trick i'll let you know if it does the trick and i'd suggest you try this also grandpaclint. thanks for all the help

 

[grandpaclint]

Re: Mercury 25XD won't start

OK well i did get it started finally it was not the reed valves i did check those the problem i believe is indeed in the carb and will try what will941s suggested. as i was out trying different things to get it started i put it in gear because when i use to start it i'd have to put it in gear usually pretty quickly to get it started. i held back the stop that prevents you from starting it in gear pulled and she fired right up i let it run a little and burn off some of the gas in there. i then put in in neutral and it started and ran fine. i believe that adjusting the idle mixture screw should do the trick i'll let you know if it does the trick and i'd suggest you try this also grandpaclint. thanks for all the help

i agree, mine would start easier in fwd,the reason is it advances the spark
just a tad, also opens the throttle a tad.
starting in fwd. is not right, or safe.
my problem was, i have a fuel enrichment start carb,(no choke)
all i ever asked on here was the procedure to start that kind of
carb.i found on the top of my carb is a round plate with a screw in the middle
under that is the enrichment chamber,there is a ****-ant gasket
that was cracked,i got a (jokingly called rebuild kit), replaced the gasket.
finally someone told me the correct procedure for starting this motor.
there is a cam that opens the throttle valve,and a small plastic roller
i wrapped that with just enough tape to tick the throttle open.


now it starts pretty good

 

[killforfood]

Re: Mercury 25XD won't start

These motors whether it's new or old shake rattle and roll at idle,

If I could get my 25XD to idle (without loading up), I wouldn't need a trolling motor. Oh well, I guess it's just the nature of the Beast.

I went through my 25XD carb last night. It surprised me too see that even after sitting idle for a few seasons and running gas with ethanol, it was sparkly clean inside (I always run it dry). My first thought after you said you had spark and good compression was that our crappy ethanol fuels had gunked up your carb.

Hope you get it sorted out.