Same old story....my Westerbeke W30 (1979) was over heating when driven hard.  I thought about pulling the Heat Exchanger or the Oil Cooler out and doing an acid wash but I opted for the another method of cleaning that I've never done before.  See Engine To Hot.

As shown above, I connected an old AC Pump up with the pump output going to the Oil Cooler Raw Water input port.  The rear Raw Water output hose on the Heat Exchanger was extended to reach the front bucket.  So I had a static engine raw water closed wash system connected.  Well closed except for the open bucket for water to be pumped into and out of. 

So after priming the pump I had a very weak water flow returning to the bucket.  Maybe ok for low engine RPM but when the engine speed increased the Raw Water exchange just could not remove enough of the heat from the cooling system.   My problem of over heading was an obvious lack of raw water volume.  Just engine age and stuff in the exchangers.

So with the pump running and with just enough water in the bucket to allow the intake hose to be submerged, I added an equal amount of RYDLYME MARINE Biodegradable Descaler. Within minutes, the water flow back into the bucket from the heat exchangers was at full flow.  I let the pump with the RYDLYME MARINE solution run for one hour.  I finished up by pumping through a bucket of clean water and reconnecting both of the engine hoses.  What a difference!  I can't believe how much water I had out the stern exhaust when I cranked the engine. 

Check out the data on this RYDLYME MARINE descaler and give it a try yourself.  This will be on my ever-growing list of things to do each year.