It could have a blown head gasket or a hole in the piston if it cranks and dies. Please clarify you question. Does it run for a little and slowly dies out? That could be a bad fuel connection allowing air into the system.
The 15 horsepower Mercury outboard motor does not have a water pump. The outboard motor is air cooled and does not have a need for circulating water.
A Mercury outboard water pump is a engine cooling system. A outboard water pump is what blows steam through to get the car cool,
Because the water pump on an outboard engine consist, in part, of a rubber impeller, dry running causes almost instant damage. In as little as 30 seconds the impeller can become unservicable. A run with no water for one minute or longer, in plastic housing applications, begins housing melt down and powerhead/seal damage. It is not good practice to run your outboard without water.
you will die.
While there are several causes of overheating, the two most common reasons, by far, would be a damaged or worn water pump, and or a faulty thermostat(s).
Most outboard boat motors are water cooled to my knowledge
Lack of water
Ozone has a direct affect on water. Ozone depletion causes water organisms to die.
does the lower unit need to be removed to replace the water pump on a 1995 Johnson 115 hp outboard engine
No gas?
carburetor or spark plugs
White