First, is this an OS 46FX or an OS 46LA - that will determine how to deal with this problem.

If it's an FX:
Most "LIKELY" you are looking at an engine with a rich setting for the low speed needle valve, or running very rich on the high speed needle. This is not hard to fix, but being new you might want to wait until you can get some help doing it. An experienced flyer will only need a few minutes to make the adjustments.

The low speed needle valve is a recessed screw inside the shaft your throttle control arm is on. I have three of these engines and each responds differently to adjusting this screw. On one of these engines it seems like all I have to do is place the screw driver in the screw slot and lean or turn very lightly on the screw to make a difference. On the others I only turn it an 1/8th of a turn. DO NOT DO THIS WITH THE ENGINE RUNNING!!

Also, make sure you have the high speed needle set right before you adjust the low speed needle. But seriously, I was much better off having experience help with this the first times I did it than going alone. It's easy to get it "ALMOST" right, and then have problems with a too lean engine in the air.

If you have an LA you use an "AIR BLEED SCREW" to make adjustments and I will leave advice on that to another with more experience as I've not had to do much with my one LA.

I would hope you can get experienced help with this before you fly. Good Luck
DickB