guys i opened and cleaned my carburetor as per suggestion of some members.Now i need to do setting(rpm screw).does any1 has knowledge how to adjust that.right now when i pull it starts some time,some time it doesn't,some time it starts in full rpm.i noticed one thing.when i pull to start the outboard.i can easily pull the rope and the outboard starts.sometime when i pull the rope it is little hard to pull and outboard doesnt start.let me know.thx
guys i opened and cleaned my carburetor as per suggestion of some members.Now i need to do setting(rpm screw).does any1 has knowledge how to adjust that.right now when i pull it starts some time,some time it doesn't,some time it starts in full rpm.i noticed one thing.when i pull to start the outboard.i can easily pull the rope and the outboard starts.sometime when i pull the rope it is little hard to pull and outboard doesnt start.let me know.thx
What year 9.8 is it? Mine (1974) only has one adjustment. It is not an rpm screw, it is the low speed idle mixture screw. The manual calls for a starting point of 1.5 turns out from fully seated. To fully seat it, gently screw it in all the way until it gently seats. Note I used the word gently twice. You don't want to crank on it and damage the needle valve.
Then, once you get it started, let it warm up. Then turn the screw out in increments of 1/8 turn waiting several seconds between adjustment. When it begins to run rougher, stop that adjustment. Then begin to turn it in 1/8 turn at a time, again waiting several seconds between each 1/8 turn. It will get better, and then will get to the point where it gets worse again. Remember how many turns (to the nearest 1/8) that you went from the furthest out to the furthest in. Your sweet spot should be 1/2 way between the two - fine tune from there, again waiting a few seconds between adjustments. Your goal is to have the idle rpms as slow as you can while still running smoothly and not killing.
Oh, by the way, this is best done in the water (or barrel) in gear - i.e. under load. I use a tub, but use reverse gear instead of forward because it doesn't kick as much water out of the tub.
What year 9.8 is it? Mine (1974) only has one adjustment. It is not an rpm screw, it is the low speed idle mixture screw. The manual calls for a starting point of 1.5 turns out from fully seated. To fully seat it, gently screw it in all the way until it gently seats. Note I used the word gently twice. You don't want to crank on it and damage the needle valve.
Then, once you get it started, let it warm up. Then turn the screw out in increments of 1/8 turn waiting several seconds between adjustment. When it begins to run rougher, stop that adjustment. Then begin to turn it in 1/8 turn at a time, again waiting several seconds between each 1/8 turn. It will get better, and then will get to the point where it gets worse again. Remember how many turns (to the nearest 1/8) that you went from the furthest out to the furthest in. Your sweet spot should be 1/2 way between the two - fine tune from there, again waiting a few seconds between adjustments. Your goal is to have the idle rpms as slow as you can while still running smoothly and not killing.
Oh, by the way, this is best done in the water (or barrel) in gear - i.e. under load. I use a tub, but use reverse gear instead of forward because it doesn't kick as much water out of the tub.
Thx for the great info.u r right there is only low speed idle mixture screw.i thought that is called rpm screw. I will try out tomorrow and will let you know.Also i mentioned about pulling rope is some time hard and some time normal.as i mentioned when i pull and it is hard the motor doesnt start but some time when i pull it is very easy and with less effort it most of the time start.so is there any thing wrong with it.let me know.thx
I forgot to reply.Here is what happened when i tried to adjust idle screw.
I tried doing setting as per above instruction.But some time motor started.even if it started it start's in full rpm.when i lower it to near idle it stops.But some time i pulll and it dosent start at all.
One thing i noticed.When i try to pull rope and it pulls very easily,it starts in first pull.But when i pull and feel the rope hard,the motor dosent start.not sure what problem is.please let me know.thank you
That's normal on the pulling as when it starts, you are no longer turning the motor over with the rope. Start with the idle screw 1 1/2 turns out. My manual says 1 out but that won't work. Mine is a 1967 with the old style carb. If it is starting wide open, that means your throttle is wide open or your advance plate is sticking. Let the motor warm up, turn the screw counter clockwise in little bits till is starts to flood out. Then turn it clockwise till it wants to stop...then remember where 1/2 way between these circumstances occur and turn it back counter clockwise to that position. This will work if everything else is ok..ie,clean carb,good fuel,good plugs/coils, good compression etc.
Mercury 9.8Hp Carburetor setting
Linear Mode
