It's on page 58 in my Perkins engine manual. Says "Adjust idle speed to 625 Rev/min". . . . . . "but idle speed may vary based on application."
I have mine set at 600 rpm's, (because we're often fishing and a little lower idle speed is better for that purpose.) But I usually idle the throttles up to 800 rpm's for docking. Makes the boat control response a little quicker and it's still within the shift RPM spec's for the BW Velvet Drive Trans.
That engine can idle quite low and usually not stall, even down to around 500rpm. Set it where you like it. Most are between 600 and 700. Too low and it stalls on shift and shakes. Too high and it bangs into gear.