Johnson 9.9 runs rough and won't idle

[outdoorsman37]

Hello! please help. i have a 70's johnson 9.9 and i finally got it to start but only when the throttle is full. it won't idle and runs likes it is missing. i checked the compression and it is fine. i changed the plugs to new and that did nothing. i am thinking it is the points under the flywheel thing on top? the ignition coils are brand new. the only other thing i would think it could be would be carberator or wires not hooked up right. any ideas? also it spits white smoke when misses and the exhaust spits out grey sludge and it is covering inside the prop. it seems like it is timing but i don't think you adjust timing on these motors? any help would be greatly appreciated. also, it wasn't pumping water so i pulled the lower end and am going to replace the water pump and impeller. i don't think that is the cause of the problem though. thanks!

 

[Rick.]

Re: Johnson 9.9 runs rough and won't idle

Well it could be a few things. White smoke is usually an indicator of water in the cylinders. Yes it could be your carb. First re- do a compression test and let us know the numbers. It could be that you need to richen (counter clockwise) the slow speed needle to get rid of a sneeze (which many call a miss). Best of luck. Rick.

 

[outdoorsman37]

Re: Johnson 9.9 runs rough and won't idle

thanks. the compression was a little over 100 on each cylinder. i know that is a little low but hopefully it is adequate. is the slow speed needle the knob on the port side or in the front? i richened the front knob all the way. the knob on the side doesn't turn much. thanks!

 

[jesusn]

Re: Johnson 9.9 runs rough and won't idle

my 83 jonhson 70hp did the same thing the stuff coming out the ports is unburnt carbon,oil,gas, you have a carb problem pull carbs rebuild yourself cus you cant trust mecks , put back to specs and you will be good to go

 

[Scottycat]

Re: Johnson 9.9 runs rough and won't idle

Here is my personal check list:

Drain your tank, carbs and lines, start with fresh high octane gas and synthetic 2 stroke oil
Change your plugs
Check your plug wires, any break-down, change-em

Still bad?

Start with the carbs, strip'em down, carb acid, rebuild, reset.
Still don't work?
Timing, carb adjustments, linkages.
Still don't work?
Shoot it!!

 

[Rick.]

Re: Johnson 9.9 runs rough and won't idle

A little over 100 and even is good compression for what I assume is a rope start 9.9 motor. The knob on the port side is a cruise control knob or idle speed adjustment. Your needle is on the front. I would suggest turning it all the way clockwise until it seats lightly and then back it off 1.5 turns. From there if it is sneezing back it off about 1/8 th. of a turn until it stops sneezing. Rick.

 

[jimdd810]

Re: Johnson 9.9 runs rough and won't idle

my 83 jonhson 70hp did the same thing the stuff coming out the ports is unburnt carbon,oil,gas, you have a carb problem pull carbs rebuild yourself cus you cant trust mecks , put back to specs and you will be good to go

should be carefull you might need advice some day and people dont forget. There are alot of us mechanics on this forum!

 

[jmendoza]

Re: Johnson 9.9 runs rough and won't idle

Carb does sound suspect. Point about doing it yourself has merit as you then know exactly what was done. I think many people have been stung by supposed mechanics who either shortcut, or just fail to do the work properly, then there are the ones who bill you for services never rendered. I think the point was if you do it yourself, it eliminates those issues. Sadly, there are a few mechanics out there who take advantage of peoples mechanical ignorance, and give the rest an undeserved bad name.

 

[kenmyfam]

Re: Johnson 9.9 runs rough and won't idle

Carb's should be serviced as a matter of routine maintenance. How about the impeller as well before putting it into service.

 

[Rick.]

Re: Johnson 9.9 runs rough and won't idle

I think we all need to be mindful of what we say and how we say it. I appreciate all who contribute to this forum. On this particular thread outdoorsman37 has heard from some very knowledgeable forum members and he will have to, as do we all, separate the wheat from the chaff. It is difficult to repair engines through cyber space but I think this forum has a proven habit of doing just that.