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Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 10964
Experience:  40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
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Cooling system check on 1997 Yamaha outboard 115

Customer Question

Is there any way to check the cooling system on a 1997 Yamaha 115 2 stroke outboard? I pulled out the thermostats and they appear a little corroded. But open and close with warm and cool water. Want to make sure that water is making it to them. The pee stream seems to stay cool when the motor is running.
Submitted: 5 years ago.
Category: Boat
Expert:  Tan replied 5 years ago.

Hi my name is Tan I will assist you.


If the cooling system is working properly then engine will not over heat and the water indicator will flow a strong stream of water. This in itself is the test. The engine has a temp sensor on each cylinder head that monitors the engine temp. If the engine over heats the engine over heat alarm will sound. Then the tell tale is the visual indicator that the engine is pumping water. These are all you need to determine that the cooling system is functioning properly. If you want more info on the cooling system as to temp you can use a Infra red temp gun to check the temp while running through out the rpm range.


If you follow the maintenance recommendations you will have a trouble free motor. The engine should be serviced every 100 hours of use or once a season or which ever comes first.

Customer: replied 5 years ago.
Should the water coming out of the pee hole be warm or hot. My water with the ears on it stays cool.
Expert:  Tan replied 5 years ago.
The water can be any where between cool and warm depending on when the thermostats open.

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