Time it takes to prime cooling system?

[CayugaCobalt]

After a long winter, we put our boats in each spring and the outdrives and intake hoses are empty etc. The sea water pump is also empty if you have replaced the impeller. In my case its a 7.4LX MPI 1997. And I am testing for a potential bad sea water pump.

How long does it take for the raw water( sea, lake, river) to reach the thermostat?

How long to complete the circuit and exit back into the lake?

 

[racerone]

Less than 10 seconds to fill an empty block with raw water.

 

[GSPLures]

^^what he said. Just started my motor (rebuild/completely empty of water) and had water out of the exhaust in a couple seconds

 

[tpenfield]

The intake hose and sea water pump are pretty much under water, or close to it, so those will be primed within seconds. Water will reach the thermostat within 10 seconds as mentioned. You will get water out of the exhaust fairly quickly, as some of the raw water by-passes the engine and goes straight to the exhaust elbow/risers.

If you have drained down the engine block and manifolds, it may take 30 seconds or more to fill those spaces (4-5 gallons of flow required), but you will have water out of the exhaust while they are filling.

Often the residual AF from winterization will provide some initial lubrication to the impeller.

So, if you are not seeing any water fairly quickly, then the impeller would be first on the check list.

 

[Scott06]

I think i depends on the engine . My old 3.0 not long , newer boat has 5.0 takes a bit longer havent timed it but long enough it always makes me worry a bit. I would think there are several gallons in the block , BBC that you have would likely take more to fill the block