? about cooling water flow.

[vetplus40]

I am trying to get a better understanding of the water flow on my 2004 Merc 305 mpi. The diagram in my manual is a bit confusing to follow (too many arrows-with some going both directions). As such, let me ask this basic question:
If I were to drain the engine block of its cooling water and then put the boat in the water, would the impeller provide water to the engine block, or would the block remain dry until the thermostat opened up and let water into the block?

 

[tpenfield]

the engine block will fill. The thermostat cuts off water flow to the circulation pump. . . . not 100% though.

 

[alldodge]

The impeller would fill everything including the block

 

[vetplus40]

Thanks. I am still trying to get my head around the thermostat being located in the housing and not the block itself(like a car). Still missing a few puzzle pieces......lol

 

[Scott Danforth]

the thermostat in a raw water cooled boat is plumbed as a mixing valve to mix incoming cold water with residual hot water to maintain temperature.

there needs to always be water flowing to the exhaust so you dont burn your boat down to the waterline

the raw water pump provides a constant flow of water into the system and the exhaust provides a constant flow of hot water out of the system

cars do not have these issues