Merc 260 Idle change after going into Neutral

C

CRay45DB

Petty Officer 2nd Class
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Aug 7, 2011
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On my 1989 260 I/O I have started having a strange Idle issue. Start up, idles at 670, in gear 600-625, but after the engine warms up, when I go into neural, my RPM after the idle killer engages and releases goes up to 800-800. Back into gear, it's fine till I go to Neutral again, same high idle.

I screwed the barrel way out, no change. Disconnected the idle, pushing on the idle, no change.

I'm stumped by this.

Thanks
 
Bondo

Bondo

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70,524
Re: Merc 260 Idle change after going into Neutral

Ayuh,... Is the cable holding slight pressure against the idle adjustment screw,..??

If so, back the screw off abit...
 
EddiePetty

EddiePetty

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Re: Merc 260 Idle change after going into Neutral

After your warm-up period, disconnect the throttle cable from the linkage to isolate any binding from the carb to the helm. should the condition remain, look for a vacuum leak, particularily in the base plate gasket area.
 
C

CRay45DB

Petty Officer 2nd Class
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Messages
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Re: Merc 260 Idle change after going into Neutral

I did disconnect the cable, no change. Easy way to check for the vacume leaks?
 
EddiePetty

EddiePetty

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Re: Merc 260 Idle change after going into Neutral

...spray any combustible solvent (WD-40, P-B, Liquid Wrench) in the suspect area. Manifold vacuum will pull the liquid through and increase the speed momentarily.
 
NHGuy

NHGuy

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Re: Merc 260 Idle change after going into Neutral

I have the same motor, it does something similar. Sometimes the tach stays up even though the engine is going at the correct RPMs as it should be. I'd recommend putting a shop tach on there to verify your engine RPMs. Your tach might be crazy like mine is.
 
C

CRay45DB

Petty Officer 2nd Class
Joined
Aug 7, 2011
Messages
112
Re: Merc 260 Idle change after going into Neutral

Its all coming back to me now. Had a Yamaha that did the same thing and I learned the hardway not to use carb cleaner.

Havent tried it yet, but I think your on the money. (I used a photo-tact and I could hear the engine rpms go up)

Thanks
 
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