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Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 11073
Experience:  40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
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I hace a mercury 470 and there is antifreeze in the fresh

Customer Question

I hace a mercury 470 and there is antifreeze in the fresh water
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Submitted: 1 year ago.
Category: Boat
Expert:  Tan replied 1 year ago.

Hello. My name is Tan.

You don't know what you mean by anti freeze in the fresh water. The freshwater cooling on the engine is supposed to have anti freeze.

Customer: replied 1 year ago.
No in the fresh water that come on form the lake going to.the heat exchanger there is antifreeze in that water
Expert:  Tan replied 1 year ago.

Ok You will have to pressure test the engine cooling system. The most likely place is the heat exchanger. Remove the end caps of the heat exchanger and pressurize the cooling system. Do you see coolant leaking from the exchanger?

The only other place is the riser gasket is blown between the manifold and the riser. This one will usually allow coolant in to the rear cylinder.

Can you do the test on the heat exchanger?

Customer: replied 1 year ago.
How do you pressurized the cooling systems
Customer: replied 1 year ago.
The boat runs good so dont think it getting in to the cylinder no water in the oil
Expert:  Tan replied 1 year ago.

Ok that narrows it down to the heat exchanger. Those are the only 2 places the coolant can get to the lake water from the engine.

Customer: replied 1 year ago.
Ok thanks i was going fishing tomorrow will it hurt to run the boat
Customer: replied 1 year ago.
do you think some stop leak would fix it or do i need to replace the heat exchanger
Expert:  Tan replied 1 year ago.

No but you have to keep the coolant level in the engine as all the coolant is going to leak out the heat exchanger. Just keep adding water as the level goes down. Watch the engine temp when it starts to climb stop and fill the reservoir with water.

I would keep filling with coolant at this point till you replace the heat exchanger.

Please don't forget to positively rate my help as that is the only way I get credit for helping you.

Thank you.......Tan

Happy 4th.