
Marine manifolds are designed to keep boat engines cool. The standard setup for most manifolds is similar to a car, with exhaust coming out of each exhaust port and each port running to an exhaust pipe. The main difference is that each exhaust port is surrounded by water to keep the boat cool. The exhaust/water mix is then led outside the boat. If the valve is open, water can run into the piston and cause rust or, worse, break the piston.
Characteristics | Values |
---|---|
Setup | Similar to a car, with exhaust coming out of each port and running to an exhaust pipe |
Exhaust ports | Surrounded by water to keep the boat cool |
Exhaust/water mix | Led outside the boat via the outdrive or a waterlock/silencer |
Crack in the manifold | Results in water inside the motor compartment |
Heat exchanger | Seawater is used to cool down the coolant before it's circulated back to the engine |
Heat exchanger coolant | Contains antifreeze |
Seawater cooling | Works best in freshwater to reduce corrosion |
What You'll Learn
- The standard setup for most manifolds is just like a car
- The exhaust comes out of each exhaust port
- The exhaust is very hot from the combustion and gets mixed with the hot water in the manifold
- The hot coolant is led to a heat exchanger
- The seawater will run through the heat exchanger to cool the engine coolant
The standard setup for most manifolds is just like a car
The motor exhausts, just like any car, into the manifold. The 'used' water is pumped into the manifold, well away from the exhaust ports, behind a bend to make sure water does not get near the ports. The exhaust/water mix is then led outside the boat, either via the outdrive or via some kind of waterlock and/or silencer. A crack in the manifold will, in almost all cases, result in water inside the motor compartment.
When using a heat exchanger, the only thing inside the engine cooling channels is coolant. This prevents corrosion, lubes the water pump and contains antifreeze. Systems designed for seawater cooling work best when used in freshwater as it is not as aggressive to the engine parts as saltwater. Boats that are trailered or lifted out of the water drain the seawater from the system, thus greatly reducing the risk of corrosion.
Most heat exchangers run coolant in the engine but still use saltwater to cool the exhaust manifold. The seawater will run through the heat exchanger to cool the engine coolant, then run through the exhaust manifold water passage to cool the exhaust manifold.
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The exhaust comes out of each exhaust port
The motor exhausts, just like any car, into the manifold. Well away from the exhaust ports, behind a bend to make sure water does not get near the ports, the 'used' water is pumped into the manifold. The exhaust/water mix is then led outside the boat. This is either via the outdrive (if any) or via some kind of waterlock and/or silencer.
A crack in the manifold will, in almost all cases, result in water inside the motor compartment. When using a heat exchanger, the only thing inside the engine cooling channels is coolant. This prevents corrosion, lubes the water pump and contains antifreeze. Systems designed for seawater cooling work best when used in freshwater as it is not as aggressive to the engine parts as saltwater.
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The exhaust is very hot from the combustion and gets mixed with the hot water in the manifold
The standard setup for most manifolds is just like a car. The exhaust comes out of each exhaust port, which is surrounded by water to keep it cool inside the boat. The exhaust ports all run together, just like a car, and then the exhaust is run into a riser which rises above the manifold, then makes a U-turn and runs down and out the exhaust port on the outdrive.
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The hot coolant is led to a heat exchanger
This process prevents corrosion, lubes the water pump and contains antifreeze. Systems designed for seawater cooling work best when used in freshwater, as it is not as aggressive to the engine parts as saltwater.
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The seawater will run through the heat exchanger to cool the engine coolant
The standard setup for most manifolds is just like a car. The exhaust comes out of each exhaust port, and each port is run to an exhaust pipe and then out the back. The main difference in a boat is that each exhaust port is surrounded by water to keep it cool inside the boat. The ports all run together, just like a car, but have water around them to keep them cool. After they all run together, most boats next run the exhaust into a riser, which rises above the manifold, then makes a U-turn and runs down and out the exhaust port on the outdrive.
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Frequently asked questions
The exhaust comes out of each exhaust port and is then run to an exhaust pipe and out the back of the boat. The main difference between a car and a boat is that each exhaust port is surrounded by water to keep the boat cool. The exhaust/water mix is then led outside the boat.
In almost all cases, a crack in the manifold will result in water getting inside the motor compartment.
The hot coolant is led to a heat exchanger, where seawater is used to cool it down before it's circulated back to the engine. Seawater never gets near the engine – only the exchanger, which is made from alloy or a similar material that can withstand saltwater.