What is the max speed for 1999 125 HP Mercury outboard motor?
The maximum speed of the 125 mercury is dependent on the boat it is on. It can only push some boats 2mph, while other boats that are light and have a small wetted surface can run 60. To find the theoretical maximum, you should find the maximum pitch prop offered for that engine. The maximum pitch prop I can find for that engine is a 24p. The gear ratio for the lower unit is 2.07:1 . If you can turn the 24p prop at the maximum recommended rpm 5250, the fastest the boat could possibly run is 57.1 mph. The propeller is not 100% efficient, so you should factor in the slip of the propeller. With the inefficiency (slip) factored in, the boat would be more likely to run 55mph. If you can find a higher pitch prop for that engine, you can get it to run faster speeds. A 27p prop would run about 60mph.
