mercury 25 hp 2 stroke

M

MuddyGator

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Jan 26, 2010
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hey everyone, I'm new to the forum and im a stundent at UF in gainesville, FL. this motor was stored for about 6 months after the impeller blew. I had the engine serviced and the motor worked fine untill anbout 2 miles away it bogged down on me and could barely run then quit. since then i have cleaned the carb, replaced gaskets on carb and fuel pump, cleaned fuel filter, replaced fuel line and fittings. the motor would start with some effort and... ran fine and then it bogged down on the way back. i then noticed a visible spark was sparking from the spark plug wire, out the boot and over the insulation on the plug to the "nut" part of the plug. I figured one of the cylinders wasnt firing so the engine was just running on the power of one cylinder. i thought this was a no brainer. i replaced the plugs, replaced the wires. in the yard with the engine trimmed down into a trashcan filled with water and tuned the lean/rich screw. i started from about 1 1/2 turns out from seated and (from what the guy at the boat dealer i got the parts from said)and turned the screw towards rich till it started to idle rougher and went back a 1/4 turn. went on the lake ran fine for about a 4 mile run. shut down and hunted. went to leave and it started and didnt want to idle and died. then after some work and throttling it started. throttled up and it bogged down. no if this happens, the only remedy has been to shift into neutral and rev the engine a few times then go to forward and this time it worked and i ran home just fine. sometimes this doesnt work and i dont want to hurt the engine. i checked the plugs after the ride home and both looked good (actually just about perfect just a light brown). I cant figure out what is wrong with this dang thing . its weird cause it will be fine and then shut down then the next start it bogs down and dies or barely runs. I hope someone can help, thanks guys.
 
L

lug nut

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Dec 16, 2009
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Re: mercury 25 hp 2 stroke

Was the vent open on your gas tank? If not that will cause it to bog down and shut off sometimes.
 
M

MuddyGator

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Re: mercury 25 hp 2 stroke

yes it is open. also pumping the ball doesnt do anything for the most part it is hard or can only take about half a squeeze. also though, like i said, sometimes revving it some in neutral will relieve the problem.
 
C

crem1

Petty Officer 1st Class
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Aug 30, 2005
Messages
365
Re: mercury 25 hp 2 stroke

Did you get a carb kit after thoroughly cleaning the carburator? If so, then I would check the reeds
 
E

ENSIGN

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Jun 21, 2009
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1,179
Re: mercury 25 hp 2 stroke

Check the gas for water & dirt,even a new filter won't get the water out.
 
W

will941s

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Oct 1, 2007
Messages
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Re: mercury 25 hp 2 stroke

Buy a can of Seafoam, about 2 cans of carb cleaner, and a carb kit. Remove and disassemble the carb, put it in seafoam for a few days. Take it out and spray it down with carb cleaner (jets, holes, tubes, everything) and blow compressed air through it. Put it together with the new kit and install it on the motor. Follow the procedures in the manual for a link and sync and I think it would be ok. Sounds like you have a fuel pump problem/something sticking in the carb. I had the same problem with my plugs so went to the Auto store and bought a Accel High Performance plug wire kit. Costed $12 and all I had to is build the wires. Since then had NO problem with the spark. You can even touch the wire with wet hands and barefoot wile running and it's so well insulated you won't get shocked.
 
M

MuddyGator

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Re: mercury 25 hp 2 stroke

will941s said:
Buy a can of Seafoam, about 2 cans of carb cleaner, and a carb kit. Remove and disassemble the carb, put it in seafoam for a few days. Take it out and spray it down with carb cleaner (jets, holes, tubes, everything) and blow compressed air through it. Put it together with the new kit and install it on the motor. Follow the procedures in the manual for a link and sync and I think it would be ok. Sounds like you have a fuel pump problem/something sticking in the carb. I had the same problem with my plugs so went to the Auto store and bought a Accel High Performance plug wire kit. Costed $12 and all I had to is build the wires. Since then had NO problem with the spark. You can even touch the wire with wet hands and barefoot wile running and it's so well insulated you won't get shocked.
Click to expand...

thats what i did too. i dont have a vice at school to do the crimps, so i looked kinda funny standing in lowes using theirs on display. the employee just had to laugh. i have gotten the mercury ones now though. What exactly comes in a carb kit cause there are several options of kits under the carb section on the mercury marine site under my engine. also how much will one of these cost i may have my parents get me one at wholesale but if its cheap it wont be worth it after shipping.
 
M

MuddyGator

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Re: mercury 25 hp 2 stroke

and also i know i will have to re do the lean/rich mixture but did i do that right? the guy at the store said the small 2- strokes should idle a little on the rich side.
 
W

will941s

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Messages
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Re: mercury 25 hp 2 stroke

Using the vice in Lowes, thats a classic, but I would have never thought of it. The carb kits usually come all the gaskets for the float bowl, drains in the bowls, new fuel pump kit, and primer kit. It's pretty much a complete rebuild and the kit costs about $23-$30 according to where you buy it. Takes about a hour to do the job after it's soaked for a few days. Just need to regular tools you can buy anywhere. Be careful when you remove the primer assembly because in the bottem of that bowl there is a small spring with a very small steel ball that you CANNOT lose, it acts as a valve. Also with the float bowl removed, if you turn the carb right up the float needle will fall out, and the new kit does not come with one. Just make sure you remove it with the carb disassembly and keep somewhere safe for the rebuild. The specs seem right, just make sure your adjusting the carb while it's running in the water, you need the backpressure from the water that you cannot get from earmuffs.
 
M

MuddyGator

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Jan 26, 2010
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Re: mercury 25 hp 2 stroke

alright well i pulled the carb off and took it apart. i used an aerosol cleaner and compressed air and cleaned the whole thing out. also i changed all gaskets with rebuild kit. put it back on and its not much better. after this i tried to adjust the lean/rich screw and basically from all the way seated to 1 1/2 turns it runs just about the same except at about 1 3/4 turns out from seated it starts to die. i set it at 1 1/2 turns and ive still got all the same problems. when left to idle there is gasoline visible on the surface of the water. the engine does not smoothly rev up, from about 25% throttle - 75% throttle, the engine make a clattering sound that just doesnt sound good. at full throttle it seems fine but i didnt want to run it wide open for long. The cylinders didnt feel very hot to the touch after running about a mile wide open. shut down and tried to crank up and go and the engine was very hard to get started ( had to throttle it to crank with the cowling off) and then ofcourse... boggs down. at WOT we were moving about 5 mph and all the sudden WAAHHHHH takes off like a bat out of hell. any ideas? still the carb? :mad:
 
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