2002 Mercury 115hp 4 Stroke EFI high idle

[stinger]

I need help looking for a cure for this condition. Recently my engine idle started to go up to 1,700 - 1,800 rpm. Docking was a bear.  Normal idle speed is 800 rpm. The power head was made by Yamaha back then. I took it my dealer and they replaced the IAC valve (idle air control valve ) with a third party after market part. Mercury stopped making it and the Yamaha part was over $400.00. The engine idle speed is now down to about 1,100 rpm. Much more manageable when trying to dock but would like to get it down even more. My dealer said that there is no idle adjustment on that engine because it’s  Electronic Fuel Injected and idle is controlled by a computer. They will try to get in touch with the Mercury Tech’s to see how to remedy the problem but I haven’t heard back from them yet. I’m sure that there are other Mercury 115 Four stroke EFI engines that have had this problem so I’m throwing this out there to see if anyone has had this problem and how they handled it.

[choked-up]

Maybe the fuel pressure regulator? I believe you can check the fuel rail pressure .

[sherman brown]

On 8/16/2023 at 7:24 AM, stinger said:

I need help looking for a cure for this condition. Recently my engine idle started to go up to 1,700 - 1,800 rpm. Docking was a bear.  Normal idle speed is 800 rpm. The power head was made by Yamaha back then. I took it my dealer and they replaced the IAC valve (idle air control valve ) with a third party after market part. Mercury stopped making it and the Yamaha part was over $400.00. The engine idle speed is now down to about 1,100 rpm. Much more manageable when trying to dock but would like to get it down even more. My dealer said that there is no idle adjustment on that engine because it’s  Electronic Fuel Injected and idle is controlled by a computer. They will try to get in touch with the Mercury Tech’s to see how to remedy the problem but I haven’t heard back from them yet. I’m sure that there are other Mercury 115 Four stroke EFI engines that have had this problem so I’m throwing this out there to see if anyone has had this problem and how they handled it.

the motor should have an idle screw adjustment on it. take your cover off and have someone give the motor a little throttle then back it off to idle while you watch the fuel linkage andit should stop when it hits the idle screw. then with the motor running on muffs or on the water just back the screw out until you get the right RPM that you want. you may need to push the linkage as you back the screw back to make sure it is in contact with the stop to be sure you will have the right RPM when running.