open system cooling question

[jaw]

I have a 2001 5.7 mercrusier with a bravo III outdrive, it has an open cooling system on it, does any raw water from the lower unit circulate through the block prior to the thermostat opening?

 

[kghost]

No

In a raw water system (non closed cooling using a heat exchanger) the water gets sucked in thru one of three ways (see below) to the water pump impeller housing and then out the pump housing and then goes thru the power steering cooler and then to the thermostat housing. From the thermostat housing it gets distributed thru the housing, first and always it goes to the exhaust manifolds to keep the exhaust cool so as to not melt the rubber hoses..........then once the thermostat opens and allows the cold water to enter the engine it will mix and the water exiting the manifolds will be warmer with the design used on your motor. See pic.

All Bravo's use a engine mounted water pump impeller that either use a thru bottom hull pick up or a transom mounted pick up or thru the outdrive.

So if your motor has a water hose coming from the transom mount (not the transom) and goes to the pump housing then it is thru outdrive.

The number 1 in the pic is the water input, again either thru bottom hull or transom pick up or transom assembly/outdrive