6 hp merc and waterpump

[bcguy]

Just bought a 1995 6 hp merc with shifting and and gas all in the handle. I noticed water stream was intermittent. Water stream runs for 10 sec and then stops for 15 seconds on a continuous cycle for the time I have had it running so far which has been 15 minutes off my dink tied to my sailboat. I had heard that this may be due to the motor having a thermostat. How would I determine if there is a thermostat in this motor and not something to do with the waterpump/impeller?.... thanks