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sebastian manrique
sebastian manrique, Auto Mechanic
Category: Boat
Satisfied Customers: 3240
Experience:  Director Ejecutivo at Multiservicios Cruz de las Mercedes
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I have a yanmar 6ly2-ste engine. The boat is new to me. I

Customer Question

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JA: Hi. How can I help?
Customer: I have a yanmar 6ly2-ste engine. The boat is new to me. I wanted to do a coolant flush as the coolant in the expansion tank is a murky brown colour. I removed the fresh water drain cock from the side of the heat exchanger on the port side of the engine, but the drain plug along side the oil cooler when opened was blocked with a black thick sludge. The engine oil is spotlessly clean and the water in the expansion tank etc whilst black is not milky. I have flushed it a couple of times , but it is still black water coming out of the heat exchanger drain cock on start up and then it clears somewhat. How do i free up the blocked drain cock and what has caused the black colour of the coolant. I suspect the coolant hasnt been changed for a long time. The engines run at nornal temperature . ie 80 degrees celcius. Both engine readings are identical.
JA: Sometimes boat issues seem like they'll be really complicated, but end up being easy to fix. The Marine Mechanic I'm going to connect you with knows all the tricks and shortcuts. Is there anything else the Boat Mechanic should know before I connect you? Rest assured that they'll be able to help you.
Customer: no thats it.
Submitted: 18 days ago.
Category: Boat
Expert:  Virtual-mod replied 18 days ago.
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Expert:  sebastian manrique replied 17 days ago.

Hello, I am Jose Sebastian. Your automotive expert, It's a pleasure to me to attend your question. Thank you very much for trust in just answer.

Dear customer, it seems to me that the sludge that you observe may be accumulated dirt residues such as rust or old oil from a previous problem that the engine may have had, can you send me some pictures of the sludge?

Expert:  sebastian manrique replied 15 days ago.

Dear customer as a general answer the accumulation of rust inside is causing a kind of sludge is like a kind of dense liquid brown colour is produced just by the rust and this is accumulating more and more until it can get to leak, when you are like this what is recommended is to disassemble the radiator and clean it in a chemical bath although other people agree to replace the radiator completely, it is also recommended to replace the thermostat and if the engine is not overheating the pump does not have to be replaced although I recommend that if it can fail in a short time.