1994 Evinrude 9.9 dies at idle

My review of past threads didn't yield an answer, so here goes. I don't know if all of this is relevant, but here it is. I bought the motor used with allegedly low hours about a year ago. I had a local repair shop tune up and test run the engine to confirm it was in good shape. It sat for a year with Stabil in the gas. I test ran it twice during that time using a water hose for cooling. It started and ran fine. About a week ago, I launched my boat and started the engine, running it at a low speed. After a few minutes the engine began to die, but would restart with the choke engaged. I noticed there was no water coming from the P-tube and the overheat warning sounded about the same time. I rowed the boat back to shore. A test run the following day revealed no water from the P-tube. I subsequently replaced the water pump assembly and the cooling system works fine now.

During test runs, the engine would run at speeds above idle, but die after several seconds at idle. It restarts immediately if I engage the choke for a second or so. I am running new gasoline and have tried two new fuel lines from two new gas tanks. I have rebuilt the fuel pump and replaced one cracked component. The problem continued. I removed, inspected and cleaned the carburetor. I did not change any adjustments on the carburetor. When I try to adjust the idle down using the trottle stop screw, it will die before the idle gets down to what sounds like a reasonable idle speed..

What do you suggest to diagnose and cure this problem?

Re: 1994 Evinrude 9.9 dies at idle

check your compression, could have bad head or exhaust gasket, also check spark.. they will run on 1 cylinder, but not idle. you can start the engine, and with insulated pliers, or if a real man, use you hand, pull 1 plug wire, the engine will falter, if it doesn't that cylinder is not firing. replace wire, then pull the other . welcome to iboats.

Re: 1994 Evinrude 9.9 dies at idle

It certainly could be compression/spark related, but if its not hard to start and seems to have full power I would think that its more likely carburetor related.

Is there not an adjustable low idle jet on that carb? Also, if you cleaned the carb without changing any adjustments then you couldn't have cleaned out the low idle circuit completely. I have had problems with Stabil brand fuel stabiliser and have since switched products.

Re: 1994 Evinrude 9.9 dies at idle

The low speed needle is on the starboard side of the carb at the rear on top. Rough setting is 1 1/2 turns out from GENTLY seated. If the needle is in to far, it will not idle.

Re: 1994 Evinrude 9.9 dies at idle

Couple questions.

When you ran it twice during storage,did you use stabilized fuel?

Also sounds like when you cleaned the carb and did't disturb any settings,you didn't remove the idle mixture screw.

Unless you are expecting the motor to idle way too low,I think you need to fully clean the carb.

DHP

Re: 1994 Evinrude 9.9 dies at idle

Thanks for the advice. It'll a be a day or so before I can try some of it. I'll let you know how it turns out.

Re: 1994 Evinrude 9.9 dies at idle

I just bought and ran a 9.8 mercury that ran fine at higher rpm but didn't want to idle. It turned out to be the breather valve on the tank wasn't open enough. At high rpm it would vaccum the tank but have enough pump to pull over the breather valve. At idle, the pump wouldn't pull over the tank vaccum / breather valve.

Just a thought. Easy fix if that's it. Good luck.

Re: 1994 Evinrude 9.9 dies at idle

perkdp said:

I just bought and ran a 9.8 mercury that ran fine at higher rpm but didn't want to idle. It turned out to be the breather valve on the tank wasn't open enough. At high rpm it would vaccum the tank but have enough pump to pull over the breather valve. At idle, the pump wouldn't pull over the tank vaccum / breather valve.

Just a thought. Easy fix if that's it. Good luck.

Click to expand...

Thanks for the help, but I know that's not my problem. I have a manual tank vent and it's open.

Re: 1994 Evinrude 9.9 dies at idle

Manual tank vent ? The screw in the cap ?
That's what mine has and if it wasn't unscrewed pretty much all the way, i'd get these symptoms.

Good Luck.

Re: 1994 Evinrude 9.9 dies at idle

Which "throttle stop" did you adjust? I am assuming the one on the lower left of the engine? I did the same thing. Try adjusting the idle screw on the top of the carb..there is a plug on the front of the carb cover that you can remove to reach it....that is if yours is like mine..pretty sure the 94 and 95 are the same....

Re: 1994 Evinrude 9.9 dies at idle

The results are in. I backed off the throttle adjustment at the throttle cable and adjusted the idle mixture and the idle speed on the carburetor. I bumped up the idle speed first and then set the mixture screw where the engine sounded like it ran strongest (fastest). I then set the idle speed on the carburetor to what sounds like a reasonably low RPM. The result is (drum roll please ..... ) it idles and runs great!d

I'd like to thank everyone who contributed suggestions and I'd especially like to thank ddennis for pointing out how to access the idle speed screw through the removable plug. It made the task much easier.

Re: 1994 Evinrude 9.9 dies at idle

Anytime! Glad I could finally contribute a bit back to the forums!