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Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 11076
Experience:  40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
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I have a 2cyl Yanmar that is leaking seawater (1gal/hr)

Customer Question

I have a 2cyl Yanmar that is leaking seawater (1gal/hr) somewhere near the mixing elbow. I took the elbow off along with the gasket but it doesn't look like it was leaking. There is a lot of rust at the elbow flange weld but no obvious hole. where is the likely leak? and what is the next logical step?
Submitted: 1 year ago.
Category: Boat
Expert:  Tan replied 1 year ago.

Hello. My name is Tan.

Have you inspected the exhaust manifold. The leak is most likely the elbow itself. Have you tried knocking the rust off looking for holes in the elbow?

Did you try locating the leak before disassembly? If you follow the water leak it should lead you to the source.

Customer: replied 1 year ago.
I will clean off the rust and check for holes. Is it likely that the leak is in the manifold cap that is in the same location?
Expert:  Tan replied 1 year ago.

It is possible. Without seeing the components and inspecting it is hard for me to know for sure. This is a case where you have to do a very close inspection of the components. If they are badly rusted and leaking externally you have to be concerned with them leaking internally also. If the leak to the outside they can leak to the inside and cause severe engine damage by water intrusion. On these components if there is any doubt it is worth replacing any questionable part which can save severe damage to the engine.

If you can post some pics I can give you a better idea of what your up against.

Post back with questions and findings.

Expert:  Tan replied 1 year ago.

Does this engine have closed cooling or is the engine raw water cooled?