Encore has a pair of Detroit Diesel 6V92 450hp twin turbo engines. After the boat was purchased, replacing the engine fluids was near the top of the to do list. We began with the coolant in the port engine which was fairly dirty and darker then it should have been. We also wanted to to a good flushing/cleaning of the cooling system before putting the new coolant solution back in.
Drain the Old Coolant
To drain the coolant from the engine remove the filler cap on the top of the heat exchanger and then remove the drain cocks. There are multiple drain cocks on the engine, with some being easier to get to than others. I removed the two shown in the picture above. One was on the bottom of the oil cooler housing, and the other was on the bottom of the piping running down and aft from the inboard side of the heat exchanger. The Detroit Diesel 92 engine manual says the coolant capacity for this engine should be roughly 12 gallons. I was able to get that amount out from removing the two drain cocks as mentioned above.
Flush Cooling System
To flush the engine I followed the instructions from the Detroit Diesel 92 engine manual. The process was very simple. Once the old coolant was drained out of the engine, I refilled the heat exchanger tank with fresh water. When it was full, I ran the engine for 15 minutes. After that, I drained the water by removing the drain cocks, letting it flow directly into the bilge. The water that came out was still dark so I redid the flushing process another five times until the water coming out of the drains was almost clear.
Clean Cooling System
Once the flushing process was complete, I used Fleetguard Cooling System Cleaner to clean the cooling system. I followed the directions on the container which included: with the cooling system drained, add one gallon of cleaner for every ten gallons of system capacity, fill the remaining capacity of the cooling system with fresh water, then run the engine at normal operating temperature for 60-90 minutes. At a Detroit Diesel recommended continuous operation RPM of 1900 for this engine, the normal operating temperature has been 160-170 F. I ran the engine for 90 minutes at the dock (no load) at 1900 RPM. I checked the temperature gauge often and also used a laser heat gun to ensure the temperature did not go above its normal range.
Once 90 minutes was up, I reduced RPMs to let the engine cool naturally. When the temp came down, I shut the engine down and drained the cooling system. After that I refilled the system with fresh water only and then ran the engine for another five minutes. When five minutes had gone by, the engine was shut down and the cooling system drained again.
Refill With New Coolant
With the flushing and cleaning completed, it was time to put the new coolant solution in. I used Shell Zone Antifreeze/Coolant. It is a concentrate that is mixed 50/50 with fresh water. The simplest way to make sure the mixture was 50/50 was to pour in the one gallon antifreeze/coolant concentrate, then refill that same jug with fresh water and pour it in. After that process was repeated six times the tank was full.
Once the new coolant solution was in, I ran the engine again for about an hour to ensure no leaks and that the engine was not overheating.
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