Usually, this problem is caused by a worn out impeller in the water pump. If you have checked that out, dependent on if you run the boat in brackish of salt water, and is flushed properly, another cause of blockage would be the thermostat
That is the engine default code. It has to do with the regulator not getting enough water to cool it down. Those are water cooled regulators not air cooled like cars. The impellers for the cooling system should be replaced about every 3-4 years. It may still cool the motor but not enough to cool the regulator which supplies the computer to set the trouble codes.
props are available from any boat shop or on e-bay
if you prop problem is a failed rubber insert, they can be replaced by any accredited boat shop
what you need to know is the pitch of the prop as there are at least 3 different pitches depending on what you do with the boat, before you purchase on line
check that there is not a shift lock to prevent accidental movement and engagement of gears
could be a button to press first or a lever to move
ring a mercury service center and ask them
Carb is probably flooding due to a stuck float, dirt trapped in the float valve or the float valve is damaged or worn.
Only taking it apart and checking will find the reason though a stuck float can sometimes be freed by tapping the carb with something like a plastic screwdriver handle.
