350 MAG open cooling system - basics

[Mauro Brisola]

2013 350 MAG, dry joint, open/sea water cooling

I'm learning about how this cooling system works and my doubts are:

What the function of the water going through the elbow? (red arrows on picture) Older engines versions usually have just the manifold cooling water flow from downside.

The water hoses to elbows come directly from the water distribution housing/sea water pump. This "unrestricted" water flow from sea water pump going directly to elbows/exhaust won't cause a loss of water pressure/flow to the main cooling system (engine internals and manifolds)?

 

[Bt Doctur]

What the function of the water going through the elbow? (red arrows on picture) Older engines versions usually have just the manifold cooling water flow from downside.

To cool the rubber components regardless of the thermostat

The water hoses to elbows come directly from the water distribution housing/sea water pump. This "unrestricted" water flow from sea water pump going directly to elbows/exhaust won't cause a loss of water pressure/flow to the main cooling system (engine internals and manifolds)?

No, there there to cool the rubber components, see above

 

[Mauro Brisola]

Understood.

Thanks

 

[Red955i]

Sorry I may only be a "cadet" on here but the function is actually for another reason....Has nothing to do with a desire to cool those hoses, though it may cool them in the process. When you see a Mercruiser with those hoses is called a Warm Manifold motor, without them are called a Cold Manifold motor. If you pul the risers off you will see in the Cold Manifold raw water motor they use full open gaskets. In the Warm Manifold raw water motor they use restricted gaskets. Basically a 300hp engine running a 160 thermostat need about 8gpm to maintain that temperature. Both the Alpha and Bravo seawater pumps provide way more water than that. somewhere between 18-20gpm. This leaves a huge excess of cold (cool) ocean water. This water flow into the thermostat housing where the circulation pump spreads it throughout the engine to remove heat. It then returns to the thermostat housing at 160 degrees or so and mixes with the new cool seawater which drops the overall temperature. In the cold motor all of the water (heated and excess) flow into the bottom of the exhaust manifolds, put through the risers and elbows and out of the boat. In doing so Mercruiser found that the average water temperature entering the manifold was often below the threshold needed to avoid forming condensation in the exhaust. So they invented the warm manifold system. Some boats are still made cold as there is no way to implement warm based on their new design. But the basis for the warm design is they can basically restrict the flow from manifold to riser which allows the system to scavenge off the excess cool water not needed by the system and send it directly out the risers without ever passing it through the exhaust manifold thereby increasing the inlet water temperature in the manifold and reducing the threat of condensation. There is no worry about not having enough water pressure or supply to the motor because the seawater pumps oversupply.