Depends on how fast the boat is traveling. On a boat traveling at 30 mph it will take 30 minutes.
First, it needs to be mounted on the boat. And the boat determines how fast the attached motor will go. If the boat is wood, then it will likely float deeper in the water, and not be particularly fast. If the boat is a smaller fiberglas one, then the motor and boat will go faster. Based on much boating experience, I would say that most boats could go 30 to 35 mph with the 40hp Merc.
150MLP
E=mc2
70
25-30 M.P.H DEPENDING ON BOAT
I have a 2.7m Inflatable boat and have a 2.5hp Marriner engine the engine will allow the boat to cruise at around 8knots and that is with 3 of us in the boat.
It depends on the boat you have it on. You might go 60 mph if you put the motor on a high-performance center-console fishing boat. You might also go 5 mph if you put it on a tugboat that's pulling logs down the river.
About 10 to 12 on plane
It really depends on how big your boat is and how fast you want to go typically you want to go 20-25 while tubing so get a big enough motor to push your boat with a tube 20-25 mph
A 3HP motor can reach speeds up to at least 30 mph depending on what you are using it for.
Videos of fast motor boats can be found on boating websites along with video sharing websites. YouTube allows anyone to post their videos for free, and they have many videos of the fastest motor boat.