Detroit 671 Marine, question

I have twin 671 naturals in my boat and would like to run water lines from it to heat hot water tank (with heat exchanger). At what point on the engine do I tie in the hot and cold hoses?
Many thanks.

The Detroit pumps have a passage that is sealed with a pipe plug in the bypass section that you can use to plumb in a fitting to deliver coolant to your water heater. The bypass is the port of the pump that is connected to the thermostat housing. The pump has two other ports opposite the bypass. One carries coolant from the heat exchanger and the other delivers coolant directly to the oil cooler housing which then enters the engine and back out the thermostat housing to the heat exchanger.

It is important that you deliver the coolant coming BACK from the water heater TO THE HEAT EXCHANGER INLET so as to not disrupt the positive flow of coolant through the pump, oil cooler, cylinder block and head. You will need to plumb a "T" for this purpose if none already exists.

This method will somewhat decrease the amount of coolant delivered through the full blocking thermostat during periods of maximum heat exchange demand and should be equipped with a shut off valve or shut off solenoid to ensure maximum cooling system efficiency if the engines are to be operated under full load, hot climate conditions over long periods of time.

Additionally, because of the powerful, high efficiency flow these pumps produce, you may want to include a flow restrictor to prevent erosion from occurring in the water heater coil.

I hope this is what you needed.