84' mercury 25xd won't stay on.

manther

Cadet
Joined
Apr 7, 2018
Messages
12
Hi, I'm new here. Nice forum.
I just picked up a new to me 25xd. Serial 6535516
It ran with earmuffs in sellers yard. When it was warmed up it had 120+ compression in both cylinders.

Drove it 2 hours home, and it won't run anymore. Here's the symptoms.
If having sat for a ling time (hours) it will start for about 20 seconds. Has a low rough idle and eventually cuts out.
After that all attempts to start result in the starter disengaging because the engine has begun to fire. But it will only fire a few times and die.

My starting procedure: Prime the inline bulb, and make sure its in neutral and the gas tank vent is open.

What I've done for troubleshooting:
New spark plugs. Champion QL78YC gapped at 0.04
New gas, and 50:1 synthetic pre-mix
removed all fuel lines. Replaced with automotive ethanol safe line.
Cleaned fuel filter.
Verified fuel is getting past the quick connect, and past the fuel filter and into the fuel pump.

Found one of the bolts on the carb was loose. Tightened it, and it ran for 20 seconds again but same results as before.
Pulled plugs. They were a little wet, but not fouled in any way.

Pulled the carb. Fuel pump diaphragms are in good shape. (Previous had new one installed).
Peeked in a the reeds, they looked normal, but I didn't pull them and look at the gaps or anything.
Cleaned the carb. There was some black specs in there, not many though. main jet was clear. float needle seat was not indented to badly. Float looked to be setting at about 1" when lightly touching the top of the float needle.
Put carb back on, fresh gas, line, plugs, clean carb. Fired up and ran for 20 seconds then died.

Remembered I left the needle, low speed screw (whatever its called) bottomed out. Turned it out 2 turns from bottomed out.
Restarted, and it would not fire at all. Had lunch, came back, still not even a single fire, just cranks.
Used a bit of starting fluid, it fired up and started pulling gas, and ran for 20 seconds, and died, and repeated the same behavior it's always had.

Pulled the exhaust cover. The gaskets looked like crap, but they tore apart when I was trying to remove the plates, so not sure if they were blown or not.
I did not see any scoring on the cylinder walls or cylinders them selves.
I need to test the spark, but I'm at home by myself, and need some one to go turn the key while I look at the spark. So I will do that soon.
Any advice would be welcome.
 

Attachments

  • photo287911.jpg
    photo287911.jpg
    356.2 KB · Views: 0
  • photo287912.jpg
    photo287912.jpg
    341.7 KB · Views: 0
  • photo287913.jpg
    photo287913.jpg
    388.9 KB · Views: 0
  • photo287914.jpg
    photo287914.jpg
    420.7 KB · Views: 0
  • photo287915.jpg
    photo287915.jpg
    351.8 KB · Views: 0
  • photo287916.jpg
    photo287916.jpg
    399.8 KB · Views: 0

flyingscott

Fleet Admiral
Joined
Apr 8, 2014
Messages
8,293
When you first start it are you pushing the key/buton in to prime? Are you setting the high idle Lever for starting?
 

manther

Cadet
Joined
Apr 7, 2018
Messages
12
When you first start it are you pushing the key/buton in to prime? Are you setting the high idle Lever for starting?

Yeah I saw a sticky on starting procedure, and I don't hav some of those things on my console. I added some pictures.

I do have the ignition press-in button, but I don't think the others.
 

Attachments

  • photo287965.jpg
    photo287965.jpg
    292.5 KB · Views: 1
  • photo287966.jpg
    photo287966.jpg
    342.5 KB · Views: 1
  • photo287967.jpg
    photo287967.jpg
    385.4 KB · Views: 1
  • photo287968.jpg
    photo287968.jpg
    339.5 KB · Views: 1
  • photo287969.jpg
    photo287969.jpg
    389.6 KB · Views: 1

jbuote

Lieutenant Junior Grade
Joined
Aug 17, 2016
Messages
1,001
Looks like a "Throttle Only": button (in red square) that you can press to advance throttle a bit to start, but won't engage forward gear.
Push it in and throttle forward a little..

ThrottleOnly.jpg
 

manther

Cadet
Joined
Apr 7, 2018
Messages
12
Looks like a "Throttle Only": button (in red square) that you can press to advance throttle a bit to start, but won't engage forward gear.
Push it in and throttle forward a little..


Haha, I asked the previous owner what that was and he had no idea. I'll try it, after I get my gaskets in. Anyway to get the gaskets the quickest? A certain website thats the fastest, or anything?
 

manther

Cadet
Joined
Apr 7, 2018
Messages
12
Oh and btw I did test spark, and the #2 had a weak spark for the first few key bumps, then it stopped sparking al together.
 

flyingscott

Fleet Admiral
Joined
Apr 8, 2014
Messages
8,293
Ok leave the plugs out and swap the green coil wires from the switch box. If the spark follows the green wire switch box is probably the problem. If the spark stays with the same cylinder the coil is bad.
 
Top