Mercury 9.9hp 2stroke wont idle when warm

[miker-gr]

I just got a used mercury 9.9hp 2stroke ( around 1995 model) and although it's start and run perfectly when cold ,after 5 min of use it won't idle!
Any ideas what can possibly be the problem?

 

[MH Hawker]

i would turn up the idle

 

[miker-gr]

I will try this.
I Forget to say that when warm it's also hard to start

 

[flyingscott]

Do a compression test and spark test before anything do the spark test after it is warm. If those are good clean and rebuild the carb.

 

[racerone]

Does the motor have a thermostat , yes or no ?--------Is the motor actually warming up, yes or no ?---There is magic sometimes.---This time of the year in some places a warm outboard motor when started will COOL OFF as it fills with cold water.------If there is not thermostat then it will not warm up much.-------I am not there to make these observations, these are some of the facts.

 

[miker-gr]

I have to check the thermostat! When it's cold it starts perfectly and idles perfectly. After 5 min of sailing it doesn't idle anymore. I have already rebuild the carb. Change the spark plugs. maybe i have to readjust the low speed mixture screw. It's completely crazy. Runs perfect when it's cold and not when warm!

 

[ondarvr]

It could do that if it's running too rich at idle.

 

[tommarvin]

Sounds like a failing ignition part, a very common question in the force section.
Starts great cold at the ramp, when I run to the fishing spot it wont hot start, after 10-15 min when the failing ignition part cools down she starts.

 

[flyingscott]

The thermostat is easy to check on that motor. When you start the motor watch the pee-hole it should dribble at first then turn into a steady stream as it warms up. What was the result of the compression test. Have you tried hitting the primer when it does that.

 

[miker-gr]

Haven't made the compression test yet.
Tommarvin what part is this?

 

[flyingscott]

Those motors have pretty durable ignitions. Have you done the spark test yet? Spark should jump at least 1/2". Have you tried disconnecting the kill switches when that happens. If the primer in the carb is starting to leak or the ball got pushed into the spring it will cause the problems you are having. Simple tests need to be done.

 

[miker-gr]

Finally i repaired it! I had to readjust the "low speed mixture screw". My friend tried it today and it was running perfectly!