Logo
FULL SITE MENU

85 merc 25xd wont start, please help!

T

tsunami14

Member
Hi I have a 1985 merc 25hp xd and it won't start.
I checked the spark from the plugs to the head and they both fire. there is good compression on the pull. cleaned out the gas filter and blew through those before and after gas lines.
put gas into the cylinders.
new gas
vent is open on tank
i put the handle throttle / shift on neutral position (right?)
and pull and no joy, not even a stutter
so i have gas, i have spark
is there an air filter into the carb that needs cleaning? by the way , this carb does not have th butterfly, it has some sort of actuator that makes a hiss noise when i pull out that big square choke.
anyways guys, i sure hope u can help me out. another thing, this motor is new to me, the guy i bought it from is a family friend, sold it for a divorcing guy (good bye toys) and he couldn\t get it going either, and when he told the owner about he was surprised, said it ran good last year, took a 100 $ off the price. so i suspect this issue is a recent development.
i wonder if i am missing something simple, this is the first motor of this style i have tried to start. thanks for your help!
 
Hiss is the acceleration pump pumping fuel to start
Sounds like carb. issues
Try carb cleaner in the intake of carb if starts definitely carb issue
Gas in plug hole wets plug need air fuel mixture not raw fuel
 
If the ON/ OFF switch in the ON position? (Don't laugh; I pulled the crap out of mine once before notcing it was on OFF! Kill switches should ONLY be momentary type.)

IF that's not it, disconnect the black/ yellow tracer wire at the switch box and check for spark. Then get back to us.

Jeff
 
Thx for your response , I looked for an on/ off switch and don't see one. Where would it be, it isn't in any of the obvious places I have looked, but I wondered if it might be something simple like that
 
Opti-man-808 said:
Hiss is the acceleration pump pumping fuel to start
Sounds like carb. issues
Try carb cleaner in the intake of carb if starts definitely carb issue
Gas in plug hole wets plug need air fuel mixture not raw fuel
Click to expand...

Hi thnx for your reply. should i shoot the carb cleaner in the front of the air intake even though it isn't running? the carb cleaner i have says shoot it in while the motor is running. also, are there any plastics in there that the carb cleaner would damage, this particular stuff says use on metal only. thx
 
guyjg said:
Does the spark SNAP and jump a 7/16" gap?
Click to expand...
thx for your reply. tried the spark test again and father in law noticed top plug has less spark than bottom plug. the bottom would jump the larger gap but had to get closer with the top plug. time for new plugs? i am picking some up today
 
tsunami14 said:
thx for your reply. tried the spark test again and father in law noticed top plug has less spark than bottom plug. the bottom would jump the larger gap but had to get closer with the top plug. time for new plugs? i am picking some up today
Click to expand...

hi i tried the new plugs, nothing different. i have noticed that the top cylinder plug was dry after trying again, and the bottom was wet (at least, the ends of the plugs were). no gas to the top cylinder = ?? shouldn't it fire just on the bottom cylinder?
thx
 
When an ignition system on an outboard is forced to jump a 7/16" gap as a real spark test, then you will hear the snap.-------Laying plugs on the block is not a very good test.
 
Still sound like a carb rebuild is needed or at least a good internal cleaning these engine I've seen run out of the water on one cylinder
 
Belive it is time for a carb teardown, cleanning, and rebuild. Probbley replace the fuel filter and hoses while at it. If motor was not run dry of fuel, and setup for storage correctly (fogged) the fuel and etheinal will gum and eat things up in a short time. If someone has also messed with the timming link and has the linkage out of time and sync will cause problems. Best bet is to buy a Manual for the motor and start from the front to the rear checking everything.
Oldman570
 
hi i
fastjeff said:
If the ON/ OFF switch in the ON position? (Don't laugh; I pulled the crap out of mine once before notcing it was on OFF! Kill switches should ONLY be momentary type.)

IF that's not it, disconnect the black/ yellow tracer wire at the switch box and check for spark. Then get back to us.

Jeff
Click to expand...

Hi i did get the unit to run for about max of 30 secs thus far. i said earlier that i had good compression , i was only gauging by the resistance when i pulled it over . guess that doens't count for much, a buddy suggested i test the compression , so i bought a tester and i got 100 and 100.5 . i tried it again after much pulling and trying different approaches after i took the carb off and reinstalled, comp is now 104 and 107. is that too low to cause firing in the cylinders? there is lots of gas getting to the cylinders, when i pull a few times and take out hte plugs to check, they have new gas on them.
any idea why this unit is only doing short runs of 5 - 10 secs? and of course, to add more to the issue when it did run 30s that time, i noticed no telltale water so i picked up a water pump to replace it. lol, what next !
 
If the throttle was wide open for those numbers then ithey are not the best. You want to see 115-120 PSI. It's 27 years old but should fire. Have you rebuilt the fuel pump? If you are not going to take the carb apart and give it a good cleaning then drain the fuel from it and the fuel line from the tank. Stick the tank end into a can of Seafoam and pump the primer until the ball gets hard. Let the engine soak for 48 hours and then see if it will fire. Make sure the idle mixture screw is set 1.5 turns CCW from fully CW w/out bottoming out the screw. It will smoke like a steam locomotive when it runs until all of the Seafoam burns off. Let it run for 5-10 minutes at more than idle speed and then adjust the mixture.
 
guyjg said:
If the throttle was wide open for those numbers then ithey are not the best. You want to see 115-120 PSI. It's 27 years old but should fire. Have you rebuilt the fuel pump? If you are not going to take the carb apart and give it a good cleaning then drain the fuel from it and the fuel line from the tank. Stick the tank end into a can of Seafoam and pump the primer until the ball gets hard. Let the engine soak for 48 hours and then see if it will fire. Make sure the idle mixture screw is set 1.5 turns CCW from fully CW w/out bottoming out the screw. It will smoke like a steam locomotive when it runs until all of the Seafoam burns off. Let it run for 5-10 minutes at more than idle speed and then adjust the mixture.
Click to expand...

hi guy, thx for your response. i will look for that seafoam and do as you suggest. one related question , i cant throttle this unit up unless i put it into gear as the shifter is built into the handle. and when i tried to open it and pull for the compression test, i coulnt pull it over , it was too tight. is it possible that the rings will loosen up with some work ie me pulling and then having intermittent running?
thx again.
hey, can u buy seafoam in canada? crappy tire maybe?
 
Disconect the linkage rod to the carb on the side of the motor and wire it so the carb is open and the shifter and tiller are in netural for compression test. A can of Power Tune can be bought at most good dealers and works for decarboning piston, rings, and cleaning the carb. Follow the directions on the can. Usally less than $15. Check the spark to see if it will jump a 3/8 in. gap and use a spark tester desined for that as all the plug wires should be grounded in so way as to not ruien the switchbox or other electrionics on the motor. A OME manual for the motor is the best thing you can buy when working on a motor you plan on keeping. From what you have stated the motor should be a fair running motor when it is cleaned and tuned up and the water pump impeller checked or replaced. If it has run for and time at all the carb, fuel pump. an filter and all fuel lines and conections should be the first place to start if you get good spark.
Oldman570
 
Maybe I missed it but have u removed and Thoroughly cleaned out carb??? Sounds like it really needs it u have spark, compression is good sounds like u are missing the final Necessity to run an engine FUEL (could be timing) not likely
Primer ball will work as temporary fuel pump to start engine if carb is clean ready to deliver fuel
 
ok thx, i will be replacing the impeller this weekend, have bought the seafom. when i go to start the motor after those 48 hours, will it start on that seafoam stuff or do i reconnect the gas tank.
 
thanks, I will set up that seafoam 'bath' tomorrow. when i change the impeller , does it make any diff which way the vanes go? i know kyou turn the driveshaft clockwise , so that means the vanes should all be trailing to left? or does it matter at all? thanks again
 
Put the impeller on the shaft.---------Lower the housing down, while turning the shaft the way the motor runs.---------That is the best way to install any impeller.
 
well guys, great news! after the 2 day seafoam bath, u could hear that motor just wanting to start when I (and a helpful neighbour) pulled away. then i thought that maybe not enough 02, so held the side connector open when i pulled and voila, she took off like nobody's business. we spent a while adjusting the connector so their would be an easy start, and now she runs on first pull! and ... lots of water from the telltale, no need to change the impeller (at least not right now although it would prob be a good idea) . many thanks boys for your advice, i learned quite a lotfrom this challenge and appreciate your support. now we'll see how that merc pushes the lund this weekend :)
 
Back
Top