Low Idle speed question

[Halfhitch]

I have two 115hp four stroke Yamahas. 2003 year model. Both motors start up fine but want to idle at 600 rpm. The Yamaha specs call for 750(50+ or -). Not a huge deal except that when cold at start-up when launching and manuevering to the dock, the port engine will occasionally die. It starts right back up but I'm sure if it was clicking just a little faster that wouldn't happen. Each engine has just over 1000 hrs.
I haven't checked fuel pressures yet. I'm just wondering if, on reading those symptoms, what would be your first guess about to investigate to get the idle where Yamaha says it belongs?

 

[wspitler]

I’d get the Ydis software and cable to troubleshoot. Not expensive. Look for TPS (throttle position sensor) setting/voltage. If this started all at once or over time, look at rigging as well. The YDIS can tell you a lot and test several components. Not likely to be a major issue on both engines, did they both show the lower idle at the same time? If they run good at higher power, not likely fuel.

 

[Halfhitch]

Thanks for that Bill. They have been that way since I bought the boat. I see in the paperwork that the previous owner had the injectors cleaned and a couple replaced at one time, but it was several years back. Both engines run good from idle on up. It's just the idle itself.

 

[Ekea]

do those engines have idle air control valves?

 

[Halfhitch]

do those engines have idle air control valves?

They have an idle speed control assembly. There is also a throttle position sensor. Before messing with them I am trying to figure out why both engines would get a slow idle symptom at the same time.

 

[DennisG01]

Just for giggles, open the fuel cap and see if it changes anything. If not, remove and clean the AS valve. While it's off, blow through the tank fitting to ensure no blockage.