Join Date: Jul 2000
Thanked 206 Times in 195 Posts
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First check for a stuffing box that set too tight!
Then start with a bucket and a stopwatch. Run the engine at your ''crusing'' rpm and measure/verify the volumetric water output at the exhaust outlet ... about 3 gallons per minute. If less, then you probably have a restriction in the circuit (piece of broken impeller stuck in the circuit, pinched hose, worn lobe/cam in the water pump, etc.). If approx 3 gpm, then consider to ''desalt'' the heat exchanger - use a non-acidic/non-destructive ''descaler'' such a Marsolve, RydLyme, etc. ... just pump it through, let sit, etc. Do the descaling on BOTH sides of the cooling circuits - fresh water and raw water sides. You can use an acid to ''pickle'' but risk dissolving the cast iron of the block, etc.
Hope this helps.