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Mercury 1988 25hp outboard question.. novice here, much appreciated.

B

bosoxer

New member
Hello and thank you. My outboard has difficulty starting at times. It's almost like it isn't getting enough fuel.. and once it does start, it seems to want to die in lower gear or when idling. Sometimes it seems to start fine and I can get it into higher gear and it runs smooth and strong, but once I power down it starts to run a little rougher and stalls out, then I have a difficult time getting it started again.. it seems to want to start with the choke out, but when I try to push the choke back in, it bogs down and stalls out again. I am running new fuel, water pump running good, replaced spark plugs and lower unit oil. I do have an older metal gas tank, which I just replaced the tubing on, but not the fittings. The tank itself looks good and shiny on the inside. Do you think this is more likely an issue with my tank/fittings or possibly a carburation issue, and what do you guys recommend to fix this problem? I truly appreciate any advice. Thank you.
 
...it seems to want to die in lower gear or when idling...but once I power down it starts to run a little rougher and stalls out...
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It sounds like a carburetor issue. Have you tried adjusting the mixture screws to smooth out the idle? If that doesn't work the idle circuits are probably clogged. I would rebuild both carbs.
 
Do you mean the choke knob, which you can turn to adjust the idle on the motor? I have tried turning that, but it doesn't do anything at all. I'm new to this whole thing (and learning alot very quickly), but getting frustrated. On the choke/idle knob, what would the "neutral" postion be? all the way counterclockwise.. then turn clockwise to adjust idling? Thank you again.
 
I think it only has one carburetor , yes !!--------------Start your trouble shooting with a compression test and check that you have spark that will jump a gap of 3/8" or better on both plug leads.---------------Once you establish the condition of the engine and ignition systems you can look for " fuel issues ".----------------------The carburetor simply responds to air being drawn thru it , and if the motor is not doing that you can not adjust for that in any way.
 
Do you mean the choke knob...
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Is there a screw w/a spring coiled under it on the carb? That's a mixture adjustment screw.

On the choke/idle knob...
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I believe that would be the choke fuel control used for starting the engine. Don't know about which direction is full choke. I'm not familiar w/this motor.
 
I do not believe the motor has a " choke plate " in the carburetor .-----It has a primer assembly which is activated by that knob when you rotate it.------------------------Try pumping the bulb on the hose after you set the primer for start.
 
Just wanted to say a big thank you to racerone and guyjg for the replies to my post. As a novice, I have done a few things that I was comfortable with, to no avail.. so I took it to a boat/motor shop today to further troubleshoot the problem. I'll let you guys know the outcome. Thank you very much again.
 
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