the problem is the idle.when you start the motor it should idle at about 600 to 700 rpm.but sometimes it idles all the way up to 1100 rpm.we tried shutting the motor down then starting it back up and that sometimes works.but usually it wont idle down until you bang it into gear.the dealer looked at the motor once already.and they adjusted the idler plates per yamaha and that made no difference.any ideas would be apprediated.

Never, never, NEVER put your Yamaha into gear at 1100 rpms.

This is why Im reluctant to purchase used equipment. You never know how some folks treat their rigs.

thanks for the heads up.do you have any idea what is wrong with it?

Did not say if this was carbed or EFI. Assuming carbed,there is an idler stop screw to adjust the
at idle RPM. However,if that was already adjusted,it could be a lean condition caused either by a
dirty carburator ,or a bad gasket causing the motor to be sucking excessive air,leaning out the fuel air mixture.

I'm pretty sure the 150 is fuel injected. While there is a throttle plate, it moves only to let more air in as you apply power. The idle is set electronically by the throttle position sensor (TPS) under controlled conditions. If your service center did what you say, get a real technician. By the way, shouldn't this topic be in "motors"?