How do you fix 150 hp mercury outboard motor that is missing from to much idling?

The first thing I would try is what we used to call a Polish Tune-up: fill up with fresh gas, mixed with oil if you need to do that, put the boat in a large body of water and run it at about 70-percent throttle for a few hours. This will clean the crud off the spark plugs and, many times, will solve the problem. If that doesn't work, do a complete tune-up.