RAW WATER SYSTEM COMPONENTS

Before I lose your attention - the key idea is that somewhere along the way the raw water hose changes from 1" ID to 3/4" ID. That's what this photo is about.
Shown here are most of the components of the raw water line - but not in their proper place. The water comes through the hull and into the raw water strainer (A), which has a 1" ID hose in and out. Next is the transmission oil cooler (B), which also has 1" ID hoses (the hoses shown are not the raw water hoses, but the smaller transmission oil hoses) . But the engine heat exchanger, not shown, has 3/4" hoses in and out for the raw water. Fortunately the raw water pump (C) is between the oil cooler and the heat exchanger, SO THE INTAKE FITTING ON THE PUMP IS FOR 1" ID, AND THE OUTTAKE IS A 3/4", to accommodate the 3/4" intake on the engine heat exchanger (not shown). It was always a mystery for me why the pump (see blue pulley pump on table) was rigged that way, and now I know. Incidentally, the siphon break (air vent) for the raw water system is at the top of the engine heat exchanger. After leaving the heat exchanger the raw water goes to the manifold raw water intake (D), through the manifold water chamber, and back out the manifold raw water exhaust (E), and then straight to the manifold exhaust elbow where it is injected straight into the hot exhaust gases. The additional water lock photo shows it path from that point on.
I have now replaced the jury rigged raw water pump with the Jabsco 3270 original pump driven directly off the flywheel. Basically I am having to relearn all this because it has been so long since I rebuilt the engine - but never really understood the whys of the 1" ID to 3/4" ID hose switch, so it's a good thing. I ordered the two fittings ($43) for the new pump from Jamestown distributor.