1989 Yamaha 150 EFTX races when idling

1989 Yamaha EFTX 150 HP 2 stroke has been running fine (once started) – until this past weekend it suddenly began racing at around 2000 rpm with the cable control arm in the neutral (idle) position, and I couldn’t get it to calm down except to basically kill it with the manual choke. Checked all the mechanical linkages and could see that the throttle arm is being moved through its entire range of motion. Ran the engine sufficiently long in my non-expert opinion to probably eliminate temporary engine flooding on start-up as a possible cause. Also tried adjusting the throttle screw stops so the throttle arm rests as close as possible to the engine block when the control lever is in idle position. I know next to nothing about outboards but can see how this could be a carburetor problem. This is the third season I’ve had the boat and I’ve not had any carburetor work done on it – and I don’t know the carburetor repair or service history.

Possible related problems/symptoms:

1. Stubborn start up recently. Have had to crank a lot, and don’t seem to get the right combo of choke, fuel bulb prime, etc. to get a quick start. In fact, I’ve noticed that when I hand pump the fuel bulb it doesn’t seem to firm up as I imagine it should.
2. When engine is in tilt up position between uses some mix oil collects in bottom pan of cowling. I’ve been told this could be coming out of the carburetor itself.

Any ideas what's going on? If the problem is the carbs, what kind of costs should I expect to replace/rebuild?
Thanks,

[jb123]

pull off breather box and ensure all butterflies are working with linkage, sounds like you may have lost a screw in one or more.
then ensure they are working with throttle.

in an 89 i owned i used to choke sometimes when running and the motor actually sucked/broke the butterfly in half ,luckily parts hung up at reed.

Breather box?

JB:
Thanks for the tip. Sorry not sure I t know what/where breather box is. Is it the vertical cover of the carb assembly at front of engine?

[jb123]

black plastic on front of carbs so you can see inside.

Thanks for the help.