Im not entirely sure what you mean by launching it, you mean from a trailer? if so then no, a boat should never be started when it is out of water unless you really know what you are doing, 85% of boats need the lake/river/sea water for cooling the engine. there are some boats that have a closed cooling system that can handle the cooling for a small amount of time but it will eventually need lakewater.
before you get it wet so if there is a problem you can remedy before you have to pull the vessell back out
Before launching your boat at a boat ramp, you should park your vehicle in the standby area to load your equipment and supplies. You should not enter the ramp area until your items are loaded.
One place to avoid anchoring a boat would be to not anchor it near a launching ramp.
Launching from shore.
flounder fish
Ventilate the engine compartment, if enclosed.
shut off the engine
i would look out or rosie odonald , chasing you wanting her panties back that you are using for a sail
You should let the ventilation system run about four minutes before starting the engine on a boat.
Turn off the engine.
To properly back a boat trailer into the water for launching, start by aligning the trailer with the boat ramp. Use your side mirrors and have someone guide you if needed. Slowly reverse the vehicle, turning the steering wheel in the opposite direction you want the trailer to go. Keep a steady pace and adjust as needed. Once the trailer is submerged, stop the vehicle and secure the boat to the trailer before pulling out of the water.
Insert the drain plug.