johson 9.5 missing at idle

[fbowen]

I have a 1972 9.5ph Johson that will start and run great for about 30 second then it will starts missing at idle and will die. If I can get to the choke fast I can keep runing. unlike other motors I have dealt with it will not clear up after it warms up. but gets worse. I have cleaned the carb. new plugs.set points. and runs good at high rpms.It seams to be starved for gas at idle. <br /><br />PLEASE HELP!!!!!!!!<br />FBowen.

 

[Bear]

Re: johson 9.5 missing at idle

Check your float height.<br /><br />"When reassembling, place the float back in position & replace the cross pin. Tip the unit upside down & check the float height. The now upside down unit should have the bottom of the float even with the top of the housing. If not, you can adjust it by bending the metal tab that acts as a stop for the float. Be sure that the float can move up & down freely, otherwise if it binds, the motor may run at different speeds depending on how much your boat is tipped to one side or the other"<br /><br />That was for 9.9-15 hp from: <br /> http://www.pugetsoundanglers.org/Fishing Info/Johnson 9.9_15.htm

 

[Ferrariiwish]

Re: johson 9.5 missing at idle

Check which cyl is week by taking off spark plug lead 1 at a time.If you get big drop in revs that cyl is ok.If you dont get a drop in the other(s)open up screw on carps and see what happens.Make<br />S U R E you cleaned carbs properely.

 

[fbowen]

Re: johson 9.5 missing at idle

I have checked the float and made sure it sits correctly in the carb and it was correct. I also found out that if I pull the choke about halfway out it idles perfect but when I put the choke back in the motor starts to miss again. Are there any adjustments that I can set for the choke? I pulled the fuel pump off and checked out the diaframs and they are in good shape( no holes or worn areas). I also replaced the hose,connectors and bulb connected from the tank to the motor. I pulled the plugs while running one by one and each one the motor slowed down like it should. Do you have any other ideas? I am at a loss.

 

[Bear]

Re: johson 9.5 missing at idle

"If the motor has problems staying running at an idle, you may have the idle jet too far closed, & need to increase the fuel to air ratio. To do this you need to rotate the knob counter clockwise.<br /><br />When you get the motor running close to the speed you want, then turn the idle screw knob (lean/rich) clockwise a slight amount, let the motor run for a few minutes, & rotate it slightly more in the same direction again. Doing this you are making the motor run leaner. Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting you'll find the smoothest slow speed setting."<br /><br /> <br /><br />Good luck!

 

[fbowen]

Re: johson 9.5 missing at idle

Bear thanks for your help the motor backfired from adjusting the rich lean knob and it must have cleared what ever was blocking the fuel to the carb. Now the motor is running smooth as to be expected. Thanks again, your forum has been a tremendous help and very informative.<br /><br /> fbowen