I think we all should listen to everyones advice and experiences choose what works for us collectively and not beat each other up over any of it.  Afterall that is one of the reasons we are all on here right.

 

I think he means that you are most likely not going to connect and monitor a flowmeter.

Pressure is the result of resistance to flow and would be measured in Pounds per Square Inch (PSI)

Flow is stated in units of volume over time.  Depending on the flow rate, could be Gallons Per Minute (GPM) or Gallons Per Hour (GPH).

You can have pressure with no flow, but for flow to occur, a pressure differential must exist.  Flow is always from an area of high pressure to an area of low pressure.

Not trying to stir the pot here, but, in an open loop cooling system; if a pressure gauge is installed at various points in the system, starting in the jet pump bowl, then in the cooling line just as it exits the pump, again in the cooling line as it enters the engine at the water pump bosses, in the drain plug, in each of the core plugs in the block, in both of the core plugs in the head, at both ends of the intake manifold, in the thermostat housing, in the hose just as the water exists the engine, and lastly just before the water dumps over the side; (little long winded there) you would observe that each gauge indicates a pressure drop.  The bowl would have the highest pressure and just as the water dumps over the side, it would be at 0PSIG. This is because of fluid friction.  Every hose and fitting is a restriction as are all of the passages in the block, heads, and manifolds.  The surface finish of the inside of the engine, hoses, etc. adds to this fluid friction.  The shape of the entry/exit of each of the fittings, be it squared with just a drilled hole, chamfered, or fully-radiused.  Are the fittings 45 or 90-degrees?  Drilled or smooth bends?

The question becomes, where is the correct location to take a reading?  If in the thermostat housing, everything up to that point is going to be higher pressure than what the gauge indicates.  Right before the water enters the engine would be the safest, at least the water pressure beyond that point will be less.

Cheers,

Joe

You don't need a flowmeter, install the gauge at the inlet to the head, perpendicular to the inlet flow (to get an accurate reading use a standard "T", the inlet from the pump goes in the side of the fitting, the gauge in one end, and the block at the other end), then read and record the inlet pressure at idle, at say: 2000RPM, 3000 RPM, 4000 RPM, and every 1000 RPM to max RPM while running down the lake.

Then while at home, install a garden hose to the inlet hose after you remove it from the pump. Now set the garden hose pressure to the idle pressure, and run the DUMP water onto the ground, run the hose at that pressure to fill the engine and when water is flowing freely out of the dump line, then put the bucket under the dump fitting,  and run the hose for one minute and remove the bucket, read the amount of water in the bucket, and this is how many gallons per minute the flow is at idle.

Empty the bucket and repeat at every 1000 RPM and record all of this info. You will now KNOW the ACTUAL gallons per minute of cooling water that is going thru the engine. No guessing here!

Then let the engine empty itself of water, some take longer than others, (the boat must lean back on the trailer at the angle that it sits in the water/lake), turn on the water at the full RPM pressure the motor can run and time the length of time until the water is FULLY FLOWING from the dump line. This is how long it takes to fill the system from sitting empty in the lake, to full throttle full cooling.

The first dozen times we did all of this (about 30+ years ago,) we were surprised, and that's why we don't restrict the inlet. Yes, I'm anal about everything, so I don't have to guess.  You don't have to believe me about anything, try this yourself.   TIMINATOR