2005 Mercury 9.9 four stroke

[bluechevyy]

Please help! I have a 2005 mercury 9.9 4-stroke with electronic ignition, power trim, yada yada yada, all the options. I can not for the life of me get my kicker to run properly at idle. Currently it will start with the choke on revs up high and then dies. The only way I can get the motor to stay running is standing at the motor and feathering the throttle.

Thus far I have tried the following; I have pulled the carb out and completely disassembled and cleaned all parts. The jets and all are clean. I replaced the seals in the carb and reassembled it. I do run stabil in my gas year round and have checked the fuel which is clean and free of water.

I have replaced the fuel line/primer bulb with a new one to verify I'm not pulling air into the fuel system. I have changed the fuel filter ( I did use a more universal filter that I could see through which is slightly larger vs. the original).

I spent much of yesterday messing around with the idle screw and have uncovered the fuel mixture screw to adjust that. Still no luck.

What I have is a motor that will start up and run only at extremely high rev'ing speed. If I attempt to back off the idle screw setting it idles down and dies. Also, it will adjust speed by itself. I will just get it to start running at a slightly lower idle and it will rev itself up very high.

The only thing I have noticed that doesn't seem right is the fuel filter seems to empty slightly while running (does not stay full).

Please help a.s.a.p. as I am suppose to be taking my 3 little girls to Hagg Lake for the opener today. Unfortunately, I cannot afford to take this to the shop. I am fully capable of all repairs on this myself, I just need help figuring out what is going on.

Thanks so much!

Curt

 

[CharlieB]

Re: 2005 Mercury 9.9 four stroke

Need the serial # to be sure, but some models have a nasty habit of developing an intake leak, sucking air past the intake gasket between the manifold and the cyl head.

Test by running the motor at whatever speed you can get it to run at a stabil steady speed, then give it brief light sprays of most any flammable carb cleaner or WD at the intake manifold/cyl head behind the carb. Watch and listen for any change in motor speed.

If speed changes you will need a new intake gasket. Lightly coat the new gasket with a non-hardening sealant, just a very thin coat and allow to air dry for at least 15 minutes before assembly.

Be sure to use a torque wrench when tightening the intake manifold bolts as over tightening can also contribute to leaks.

 

[bluechevyy]

Re: 2005 Mercury 9.9 four stroke

Or063010

 

[bluechevyy]

Re: 2005 Mercury 9.9 four stroke

Any other ideas out there?

 

[CharlieB]

Re: 2005 Mercury 9.9 four stroke

A carb going low on fuel can cause a rapid idle speed til it low enough the motor dies.

Temporarily install a clear hose for the fuel line between the fuel pump and carb. Start the motor and watch the clear hose to see if any air bubbles are passing thru, indicating air sucking into the system somewhere between the fuel pump and tank. Also check the fuel dip tube in the tank for cracks.

 

[Star]

Re: 2005 Mercury 9.9 four stroke

Hi Bluechevyy,
I just had the same problem on a 05 15hp four stroke. Motor would start fine but would die bellow 2000 rpm. Wet to get carb soak
from auto store but they wanted $30 for it. I got some $3.00 carb spray with the little plastic tube. I removed the carb, turned it upside down removed the 4 screws on the bowl, the float and gasket. The round brass cap has to be removed.. not the jet. Wrap the
inverted carb with stretch wrap. Wrap the red plastic tube for the carb cleaner with electrical tape until it fits snugly in the hole where you unscrewed the cap. Flood this passage with carb cleaner and let it sit, 10 to 15 minutes. One side goes to air bleed in and the other goes to the idle circuit on the back side of the throtle butterfly. Squirt it many times but be sure the electrical tape doesn't come appart. Finally blow it out with a 100# air hose and you should be good to go. Good luck!

 

[bluechevyy]

Re: 2005 Mercury 9.9 four stroke

great info guys, I appreciate it greatly. I will try this tonight and tomorrow and reply back with the results. I hope this works as this is a frusterating problem.

 

[bluechevyy]

Re: 2005 Mercury 9.9 four stroke

Alright, here is the bad news. None of these ideas worked. I took the carb off cleaned it extremely thoroughly, submerged the carb body for a few hours and blew it clean with high pressure air. I am 100% sure this carb is CLEAN. Every passage is flowing freely.

I also put a clear line on for the fuel line from the fuel pump to the carb and it is running perfectly clear and NO air in the line at all.

I sprayed carb cleaner around the gasket from the intake to the cylenar head and from the carb to the intake and there was zero raise in the idle speed. I sure there is no air leak.

The engine will run about 2000rpms but still dies when I attempt to go lower. It also revs itself up by itself and then goes back down every once in a while (every 5-10 seconds).

HELP please!!!!

Curt

 

[bluechevyy]

Re: 2005 Mercury 9.9 four stroke

Almost forgot to add, there is a constant exhaust or smoke coming out of the engine, which, I beleive did not happen when I had this engine new.

 

[Star]

Re: 2005 Mercury 9.9 four stroke

Hi again blue,
Gee I'm sorry that didn't work for you. the problem was so simalar to mine. That brass cap feeds the idle circuit if it is pluged hardly any gas gets past the butterfly until you open it. The outher passage is to bleed air through a port under that plate on the top of the carb. In the air bleeder line there is restrictor if you preasured the tube that holds the small brass mettering jet sealed with tape it should clear it out. Wen you cleaned this carb before dit you find any particals?

 

[CharlieB]

Re: 2005 Mercury 9.9 four stroke

Check the crankcase oil level and als o smell it to determine if it smells at all like gasoline.

A pin-hole in the fuel pump diaphragm will allow gas to enter the engine, raising the oil level and the fumes from the crankcase are routed into the carb air inlet. The additional fuel will cause strange erratic idle, once the crankcase is full enough fuel/oil mixture will be blown into the carb, flooding the motor at low throtttle.

 

[bluechevyy]

Re: 2005 Mercury 9.9 four stroke

When I cleaned the carb out I found no evidence of contamination in it. I also checked the oil level and it is about half way up the dipstick XXXX's with no gas smell at all. Smel just like normal oil

 

[bluechevyy]

Re: 2005 Mercury 9.9 four stroke

Any other ideas?

 

[bluechevyy]

Re: 2005 Mercury 9.9 four stroke

REALLY! have I stumped everyone with this?

 

[bluechevyy]

Re: 2005 Mercury 9.9 four stroke

Well I'm still stuck on this. I took the carb out again and scrubbed it with a tooth brush and WD then cleaned with carb spray and high pressure air. Put it back in and ran the engine. Still won't keep running at low idle. Definately not the carb. I have cleaned it better than anyone would. It runs ok at high rpms, not missing or anything, but, does seem to smoke some out the exhaust. Will not even try to idle down without just dieing though. It will randomly surge 1000 rpms or more when it's running at any speed.

Help me please I don't know what to check now.

Thanks again!
Curt

 

[bluechevyy]

Re: 2005 Mercury 9.9 four stroke

Now have checked compression and both cylinders read 150psi.


HELP!!!

 

[Star]

Re: 2005 Mercury 9.9 four stroke

bluechevy,
I know that you will not belive this but the only thing that can cause this is the carb not feeding through the idle circuit!!! Nothing else changes between
900 rpm and 2000 rpm. If you are careful with the choke setting half way I think you can make it idle roughtly in its curent condition. Something in the drilled pasage going from the metering jet to the back side of the throtle butterfly. If you cannot pass carb cleaner through the small hole next to the butterfly to the
chamber under the brass cap I said to remove then that IS your problem!! If you want can send a print from the manual. Took my 15 out on the sound yesterday it ran smoth as silk, about 10 days ago I had exactly the same problem.

 

[bluechevyy]

Re: 2005 Mercury 9.9 four stroke

That's the thing. Carb cleaner goes right through there no problem.

I did just find that the top spark plug is coming out slightly wet and was much darker than the bottom spark plug. Is it possible that I may have a coil going bad. Not getting enough power out of the coil to one cylinder? Is there a way to test an outboard coil?

Thanks,
Curt

 

[BoatNoobie]

Re: 2005 Mercury 9.9 four stroke

If you got everything else, I'm going with fuel pump.

 

[CharlieB]

Re: 2005 Mercury 9.9 four stroke

When you take the top plate off of the carb you should find a few VERY small holes that go thru into the airway just behind the throttle blade.

These holes MUST BE clear, many times I haave resorted to reaching for the very small sewing needle that I keep in my tool kit to clear these passages. Follow with a good spray solvent, then compressed air.

WARNING: DO NOT FORCE A LARGER OBJECT THRU THESE HOLES, you only want to clear any dirt obstructing the passage, you do not want to distort the metal or enlarge the holes.