2005 Mercury 90hp 4 stroke won't return to idle

[fraannk]

My 2005 Mercury 90hp 4 stroke will run just fine but when you increase the throttle the RPM's will increase but the motor will not return to idle. It just stays at the max RPM's hit with the throttle.

I took the "vacuum line"? off of the accelerator pump and my problem went away. The motor ran normally and would accelerate and decelerate normally. I put the tube back on the accelerator pump and the problem came right back.

Does anyone know if this is a problem with the accelerator pump or a problem with the tube that I think is a vacuum line?

Thanks,
Frank

 

[fraannk]

Re: 2005 Mercury 90hp 4 stroke won't return to idle

No ideas on this one huh? Anyone even want to take a guess?

Frank

 

[raymor]

Re: 2005 Mercury 90hp 4 stroke won't return to idle

Try cleaning the IAC.

 

[fraannk]

Re: 2005 Mercury 90hp 4 stroke won't return to idle

Not sure what the IAC acronym stands for...

 

[fraannk]

Re: 2005 Mercury 90hp 4 stroke won't return to idle

Ok, after studying the manual for a while I have some more questions. When you accelerate the push rod pushes on the diaphragm in the accelerator pump. That allows air to go pick up fuel and send more to the carbs. I think there might be a blockage in the tube that allows air back into the accelerator pump to make sure the diaphragm returns to normal.

Am I way off base here?

Thanks,
Frank

 

[Jeep Man]

Re: 2005 Mercury 90hp 4 stroke won't return to idle

I had the same problem with mine. Now, my motor is a 60 hp with efi, but I am assuming the linkage is similiar. To temporarily "fix" the problem, I adjusted the throttle linkage all the way in the opposite direction. I could then at least operate the boat. When coming into the dock, I was in slow speed but not idle. By shutting the engine off then restarting, it would go to idle. When I got to the dock and lifted the shroud and gave it a "good" look, I found that the throttle lever had popped out of the throttle cam. Once I snapped it back in and reset the linkage I was good to go. Hopefully your is as simple to fix.