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Old 07-30-2019, 12:59 PM   #1
City: Wilmington
Join Date: Jun 2013
Posts: 3
What is a typical for raw water system pressure?

Does anyone know what typical raw water system pressure to expect at idle and max cruising RPM?

The repair was prompted because a coolant pipe was popping out of the heat exchanger and leaking. It is sealed with o-rings but it is not held securely enough (in my opinion) to suggest that it is intended to resist more than a few PSI of water pressure. I measured an alarming 10 PSI at idle and a little more than 40 PSI at 2000 RPM. After soaking the internals of the raw water system with vinegar (overnight) and removing a few zinc bits the pressure at went from nearly 40 PSI at 2000 RPM to less than 20 PSI. The pressure at idle on both motors is now less than 7 PSI.

The leaking problem appears fixed but since the system appears to be designed for low pressure, I am wondering what is normal.

Motors are twin 135 hp Volvo TAMD40B.

thesnide1 is offline   Reply With Quote
Old 07-30-2019, 02:46 PM   #2
City: Seaford Va on Poquoson River, VA
Vessel Name: Old Glory
Vessel Model: 1970 Egg Harbor 37 extended salon model
Join Date: Jan 2016
Posts: 2,257
If engines are running at normally operating temp, and you have a decent flow out the exhaust, and its not leaking, then its good.
Your pressures sound realistic.
Pressure could rise if the heat exchanger is clogged. And you cleaned it.
The raw water pump is going to pump whatever it can in gallons per hour at a given rpm, these are not specified for pressure, more like flow. the raw water system will have little backpressure, water is just flowing in, through, then out.
sdowney717 is offline   Reply With Quote

heat exchanger, raw water pressure, tamd40b

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