[sunbird 18]

2001 Yamaha 225 (SX225TXRZ). Long story short, it idles at about 650 in neutral in the water, and idles at about 900-1000 out of the water on the hose. Is this normal? If not what could cause it?

[k4ubr]

that is normal for all outboards do that there is no back pressure (water)

[rodbolt]

actually on an EFI motor its not normal.
the ECU will control the idle speed based on inputs from the 02,sensor,crank position sensor,Throttle position sensor and the coolent temp sensor.
if the ECU sees a cold engine it will hold the idle high.
your engine should start at about 1200 RPM then as it warms up it should drop to about 700 RPM. however with no back pressure and especially if the O2 sensor needs maint it will idle funny.
your idle speed in nuetral is about 730 RPM and in gear trolling about 625 RPM.

[k4ubr]

if this where a 4 stroke that would be. this 2 stroke will idle 900-1000 out of the water. normal