HELP! 2005 9.9 four stroke mercury (almost same as tohatsu)

[bluechevyy]

2005 Mercury 9.9 four stroke
Please help! I have a 2005 mercury 9.9 4-stroke (OR063010) 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 about 4 times and scrubed parts with a tooth brush/WD40 ad Carb cleaner. The jets and all are clean. All holes flow carb cleaner freely. I even used some feeler guages where possible and gently pushed them through all of the tiny holes in the carb to ensure they are not full of varnish or build up. 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.

I also installed clear fuel line from the fuel pump to the carb and verified fuel flowing and NO air in the line.

I sprayed carb cleaner around the intake manifold to cylinder head gasket and around the carb to intake gaskets to check for air leaks and got no reaction.

I checked compression on both cylinders and both read almost exactly the same at 150psi.

I changed spark plugs. When I did run the engine I noticed the top cylinder spark plug seems to be very slightly wet and dark colored compared to the bottom one.

What I have is a motor that will start up (cranks over a little longer than I think it should and starts slowly before rpms excellerate) and runs 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.

Unfortunately, I cannot afford to take this to the shop. I am fully capable of most all repairs on this myself, I just need help figuring out what is going on.

HELP, HELP, HELP, the Mercury guys have run out of ideas to help me!

Thanks so much!

Curt

 

[pvanv]

Re: HELP! 2005 9.9 four stroke mercury (almost same as tohatsu)

It is a Tohatsu motor.

You may or may not have caused some scratching in some passages. If you did, you will need a new carb, as you will get weird mixtures at some levels of vacuum and throttle. Hopefully you were gentle enough that the carb is OK. It takes a surprisingly little defect to really muck up the mix in some cases.

As for the carb cleaning, you did not clean it yet. It sounds like it is lean in the idle and/or transition circuits. There are no shortcuts here. WD40 does nothing, and generic spray is not aggressive enough to clear the varniching from the passages. Period.

Do a complete disassembly, including jets and emulsion tube nozzle, use real carb dip (available at auto parts houses in 1- and 5-gallon cans), and do a real 4-hour soak at room temperature, followed by a blow-out with generic spray, followed by a careful reassembly. And then set the pilot mixture back where it was -- where it belongs. Otherwise, you have not cleaned the carb. Period.

In the future, always run the carb dry at the end of each day, to reduce the chances of varnishing

Get rid of the clear vinyl fuel hose. It will shrink, and get hard as glass after a while.

 

[bluechevyy]

Re: HELP! 2005 9.9 four stroke mercury (almost same as tohatsu)

good info, thanks. I just installed the clear hose for diagnostics, it's already removed. Will try the 4 hour soak tonight and report back.

 

[stormmnv]

Re: HELP! 2005 9.9 four stroke mercury (almost same as tohatsu)

follow "commanders" advise.... I have a Nissan 9.8 4 stroke that had the same problem...was almost ready to deep six it because it was almost new and no varnish... finally gave it the 4 hr. soak in carb cleaner and a full inspection (again) and found a small blockage in one of the jets.... did you remove the factory plug that covers the idle adjustment screw??? the factory has these engines leaned out and they idle much smoother when richened up a bit.

 

[bluechevyy]

Re: HELP! 2005 9.9 four stroke mercury (almost same as tohatsu)

Yes i removed the plug. I am giving a 4hour soak tonigh. I have a friend lending me the gallon solvent and we'll give it a try. I fully understand the "deep six" it feeling I feel like using it for a anchor, but, I know I can get this problem fixed. I just can't have it interupting my upcoming springer salmon fishing!!!

 

[bluechevyy]

Re: HELP! 2005 9.9 four stroke mercury (almost same as tohatsu)

Well, after being told it is for sure my carb on the last 4 or 5 posts from everyone, I did complete a carb dip all parts that were not plastic for 22hrs there is absolutely no improvement. So as I have been saying it is NOT my carb. It's as clean as it can get.

The engine starts only at high throttle still and once going smoke pretty badly and surges in rpms pretty bad (I'm guessing around 2k rpms to 3.5k rpms or more all by itself every few seconds.

Any help OTHER than it's my carb would be greatly appreciated.

Thanks,

Curt

 

[pvanv]

Re: HELP! 2005 9.9 four stroke mercury (almost same as tohatsu)

If you soaked your carb in real carb dip, sych as Tyme, for nearly a day at room temperature, you would have burned the anodizing off the aluminum, turning it a dull grey. You would have known immediately, by the appearance, that something had gone wrong.

What is the oil level on the dipstick? Is there any chance that you are overfilled?

 

[bluechevyy]

Re: HELP! 2005 9.9 four stroke mercury (almost same as tohatsu)

I soaked it for 22 hrs and it was in carb dip from autozone ($27 for the one gallon can). Why do you guys not believe me. It was 3-12-12 at 8:30PM and I took it out on 3-13-12 at about 6:30PM. My math that is 22 hrs and the carb look almost the same.

My oil level is half way up the dipstick XXXXXX's.

 

[joelc]

Re: HELP! 2005 9.9 four stroke mercury (almost same as tohatsu)

I soaked it for 22 hrs and it was in carb dip from autozone ($27 for the one gallon can). Why do you guys not believe me. It was 3-12-12 at 8:30PM and I took it out on 3-13-12 at about 6:30PM. My math that is 22 hrs and the carb look almost the same.

bluechevyy - did you find an answer? I'm having the same problem with a Nissan 9.8 I just bought, dipped it three days in the autozone carb dip, checked plugs, getting a fast idle choked, faster unchoked, and lotsa oily smoke. I had just changed the oil, so I sucked some out in case I overfilled. Got fresh gas, added carb cleaner to it, checked filter, pump gas stream to the carb ok.

 

[bluechevyy]

Re: HELP! 2005 9.9 four stroke mercury (almost same as tohatsu)

Took it to the shop finally and they identified it as a casting flaw in the carb where the float needle moves in and out. They ended up changing the carb for a brand new one and it runs fine. Something was sticking. They would hit the motor and it would run good until the float raised again.