adjusting idle RPM's

(ghostrider_2) · (ghostrider_2) **Join Date: Aug 2004** 10-15-2007, 12:52 PM

just curious how to adjust (if possible) the idle rpm's on a merc cruiser 350 (05). I don't want to take it into the shop for this.

(motobob13) · (motobob13) **Join Date: Jun 2006** 10-15-2007, 3:02 PM

The engine idle on the EFI engines is controlled by an electronic Idle Air Control Valve which is controlled by the ECM (brain). There is no manual idle adjustment. Factory setting is 900 RPM. Dealer can change that setting (from 600 to 1200 RPM).
If you have a carb idle adjustment is easy, but I doubt you do. Sorry...-Bob

(ghostrider_2) · (ghostrider_2) **Join Date: Aug 2004** 10-15-2007, 3:23 PM

its at 4600 rpms and the manual says 4600-6000 rpms. not a carb (yes thats easy) it was at 5000 rpms and now it at 4600.

(meathead65) · (meathead65) **Join Date: Sep 2006** 10-15-2007, 3:54 PM

Huh???

(motobob13) · (motobob13) **Join Date: Jun 2006** 10-15-2007, 4:09 PM

Kenny,
Do not open your engine hatch. Take it to the shop. At 5000 RPM you should be going like 80 MPH !!!

(882001) · (882001) **Join Date: Nov 2003** 10-15-2007, 7:31 PM

huh?

(rio_sanger) · (rio_sanger) **Join Date: Apr 2007** 10-15-2007, 7:52 PM

4600 rpm idle????

(rallyart) · (rallyart) **Join Date: Nov 2006** 10-15-2007, 9:10 PM

I think he means 460 - 600 RPM.
I have the Mercruiser 5.7 330hp and my idle is 550 on the tach but is 600 on a digital test tach.
It can be programed a bit different but it doesn't matter as long as it runs smooth and steady at idle after it warms. I have an 8000 RPM engine in a car that idles at 250 if I want it to.
Sometimes the idle being low causes the engine to lug when you get on throttle. If that happens you need to boost the RPM a little.

(ghostrider_2) · (ghostrider_2) **Join Date: Aug 2004** 10-15-2007, 9:50 PM

Art, you are correct I did mean 460..sorry guys, I started leave today before my deployment and started to have a little captain & crown, so I forgot how to type..

(ghostrider_2) · (ghostrider_2) **Join Date: Aug 2004** 10-15-2007, 9:53 PM

whats the long gold nut that can be adjusted on the end of the throttle cable for?

(jayc) · (jayc) **Join Date: Sep 2002** 10-16-2007, 2:58 AM

You can adjust the speed with the cable but this is the wrong way to do it as it will actually open the throttle plates. Like has been said if its EFI then the base idle is controlled by the air idle bypass which can get gummed up or just stop working.

If my idle speed wasn't right the first thing i would do is pull it and clean it out with carb cleaner.

(ghostrider_2) · (ghostrider_2) **Join Date: Aug 2004** 10-16-2007, 10:16 AM

the engine is keep pretty clean, but where is the air idle bypass that you are saying can get dirty/gummed up?

so the nut on the cable will adjust the throttle, because it was a little loose which is why I was asking.

(jayc) · (jayc) **Join Date: Sep 2002** 10-17-2007, 1:48 AM

Depends on what type of engine you have, ie MPI or TBI. Best bet is to get hold of a workshop manual as this will show exactly where it is.

On my TBI mercruiser its on the side of the throttle body. It requires 2 torx bolts to be un screwed to remove it.

(peter_c) · (peter_c) **Join Date: Sep 2001** 10-17-2007, 9:30 AM

Take it to a repair shop. Making a mistake can cost more than the repair. DO NOT adjust any screws bolts or other type adjustments. TPS voltage has a set spec and it will change if anything else is adjusted.

The only thing you can do is clean the throttle plates, but do not get any cleaner into the TPS or it can fail. The IAC should compensate for anything gummed up, so if there is a problem a computer reflash is most likely in order.

Really the best thing to do is to take to a professional.

(ghostrider_2) · (ghostrider_2) **Join Date: Aug 2004** 10-18-2007, 1:02 AM

The gold nut has a back nut on it which I found to be a little loose, I tightened, not even a quarter turn and now I am good to go..