I don't blame you, for that task is simple as pie. But your carbs can not be flooding or you'll be wasting your time, so check that first. (Easiest way to do that is match how it idles with the fuel connector removed. Most OBs tend to speed up just before running dry, but if yours idles better long before then, it might be flooding.)
Assuming the carbs are okay, do the following:
1. Warm the motor thoroughly
2. With the boat on the trailer, or tied fast to a dock (so it won't move and trick you) put it in gear
3. Take each idle adjustment, one at a time, and SLOWLY turn the needle IN (CW) until the motor starts to stall
4. Immediately turn it the other way (CCW) about a half turn. Then repeat the above for the other carb.
5. If the motor stalls when doing this, back the adjustment off, refire, and try again.
6. SLOWLY turn each idle adjustment screw one way, then the other, an 1/8 of a turn each time, searching for your best (smoothest) idle. Take your time after each adjustment and let the motor 'settle out'. Important!
7. Now that you have found your best idle setting, add 1/4 turn OUT (CC) to both adjustments.
Then take her for a ride. If the motor tends to bog as you open the throttle, add another 1/4 turn OUT (CCW) on the adjustments.
Good luck,
Jeff