If i put my 25 horsepower outboard motor on my 12 foot boat that is regulated to a 15 horsepower moter max could i be fined or lose my boat?

It,s a safety guide for safe efficient use of an outboard. The other motor may be too heavy or too powerfull to control in which case you are in charge of a dangerous craft. Some people carry extra ballast to outweigh a slightly more powerfull motor, 4 strokes are heavier than 2 strokes, sea condition, number of people in the boat, other boaters, swimmers, control and safety all need to be considered. Worry about that rather than a fine.