Mercury 2004 outboard 25hp - troubleshoot for thermostat or water pump problem?

Question

Last fall when I quit using my outboard motor everything was fine and then this year when I put the motor into use I had the following problem.

There is "NO" water coming out of the veep hole located on the back side of the motor.

Usually, the motor will start up and within a short amount of time, I will see water start to dribble out the veep hole and then turn to a steady stream, however this year there is NO water coming out of the hole.

I checked the veep hole for blockage and there was none.

I checked with the mercury mechanic and he said to order and install the water pump kit; which is about 60 dollars.

I'm thinking since there is "NO" water at all coming out, that maybe my problem is the thermostat and not the water pump.

My question is to ask for your ideas on how to trouble-shoot whether the problem is the thermostat or water pump.

your help is greatly appreciated and thank-you

Answer 1

Remove the water tube where it connects to the engine block and then start the motor and check for water flow.  You did not see a blockage but bugs can make mud nests back in the tube where you cant see. If you get water with the hose unhooked clean it out and reinstall. If still no water have the pump impeller replaced. Not very likely to be a thermostat, especially on an 04 motor.

Answer 2

Yes the problem can very well be the therostat. If the thermaostat does not open up it will not let water through. To check this take it out and heat the bottom of thermostat an see if it opens or just take it out and run your motor with out and see if you get water then. You will not hurt engine running without it. Be certified mechanic for 6 years.

Answer 3

the problem could be with the water pump.

Answer 4

I would say the water pump.  The water pump should always be working, and the thermostat would control the amount of water cooling the engine.