OB Water pressure PSI vs RPMs Chart

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OB Water pressure PSI vs RPMs Chart

Post by DaleH » 01 Aug 2016, 10:18

Added a water pressure gauge, as I like an instant readout on the impeller and cooling performance. Turns out that I "missed" a few RPMs in the range whilst taking the picture, but otherwise the comparison of water pressure PSI vs RPMs plotted pretty much dead nuts on straight line using an Excel linear progression.

Just a few sample picture shown, not all taken. Those in blue text on the chart are confirmed values, vs the red ones that were plotted by the linear progression.
Water PSI at 1200 RPMs.JPG
Water PSI at 2000 RPMs.JPG
Water PSI at 5000 RPMs.JPG
Water PSI vs RPMs Chart.JPG
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OB Water pressure PSI vs RPMs Chart

Post by onthewater102 » 01 Aug 2016, 11:09

Do you need to tap the powerhead to install one of those or can you put it in-line with the tell line?
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OB Water pressure PSI vs RPMs Chart

Post by kofkorn » 01 Aug 2016, 11:24

The ones I've seen have had a "T" fitting instead of the standard right angle fitting on the tell tale. I'm sure you could tee into the tell tale line but you're pressure readings are likely going to be lower, possibly even negative due to venturi action.

It will depend on what the size of your tell tale hose vs the size of tell tale discharge opening. If you have a tell tale fitting with a small hole, you should be able to get reasonably accurate readings. If your tell tale is simply the telltale hose routed through the housing, then your pressure readings would be very low.

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OB Water pressure PSI vs RPMs Chart

Post by Sinkingfast » 01 Aug 2016, 13:29

Looks like it is staying in displacement mode all the way given the straight line. The manual for my omc15 says as pressure increases it goes into centrifugal mode. Interesting...I wonder how the thermostat might affect the curve...
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