much more effective to circulate it, considering the cost of Rydlyme it makes sense to invest in a little circulation rig. Several years ago I made one (similar to those bucket oil changers) except I drilled a hole in the bucket near the bottom and installed a pvc ball valve. A few hose fittings and some hose and you have a nice rig that really works. Ideally you jump into the SW side of your engine at the first cooler inlet and have the return from the outlet of the last cooler. You also need to pull all your zincs as they will get eaten by the acid. Also the supply line to a shaft seal if so equipped needs to be blanked/plugged as you will dump Rydlyme out the seal there. Remember, you don't flush through the raw water pump, jump in right after the pump.can one simply closs raw water supply, add 3-4 gallons of rydlym and let sit in engine for 1-1.5 hours and flush out ? it isn't as good as circulating but is if effective ?