115 merc 1973/cant get to idle

[m.a.walgren]

i got a 1973 merc 115 , put a new rotor in it and carb kits in all carbs, timed and synced it (acording to the article by clams)now i cant get it to idle .it runs rough and then the idle will pick up when i move the throtel foward and move it back ,but then it starts to run rough again. i did notice that the bottom carb has fuel coming out of the top of the carb where the fuel goes into the needle valve and foat, also when i try to adjust the idle screw on the bottom carb i can turn it all the way in and it doesnt affect it . thanks

 

[Chris1956]

Re: 115 merc 1973/cant get to idle

Clearly the lower carb has an issue. Pull the bowl cover and check the needle and seat for proper sealing and float lever adjustment. Reset idle mixture screw to 1-1/2 turns out.

Now you need to set the idle mixture on all three carbs. it is a bit tricky to get the correct richness w/o practice. I adjust the mixture on all three carbs until I obtain the smoothest, fastest idle. It should now be too lean to accellerate well. Now starting form the top carb, I open the idle mixture needle 1/8 turn at a time while trying to accelerate the motor, in gear on the water. The sequece is try to accelerate, if the motor boggs, open the top carb idle mix screw 1/8 turn and try again. If it still boggs, open the mid carb 1/8 turn and try again. repeat sequence with the bottom carb. You will find that you will richen the top carb the most, followed by the mid carb. You are done when the motor idles reasonably well and accelerates well.