i didnt understand much but thier is pencil anodes in raw water cooling system that need to be changed often

I have just fitted a fresh water flush system to my fresh water cooled Volvo 2003 on the advice of my marine mechanic. The benifits being;

1) flush out the salt water cooled heat exchange, which will increase service intervals.
2) flush out the exhaust elbow that I have just replaced due to corrosion inside the eblow preventing sea water from discharging. Almost cooked the motor as it was completely blocked.

When I return from a day out I turn off the raw water intake gate valve and connect fresh water (from the galley sink) to clear hose that has been cut into the raw water intake line (with a three way fitting) above the gate valve.

I then run the motor for a few minutes to flush the system ensuring water is visble in the clear hose. I leave the sea water intake valve off (until the next trip) so fresh water remains in the heat exchange and exhaust elbow while not in use.

Time will tell if it is worth the effort. I did it more to prolong the life of the exhaust elbow (as they are becoming hard to get) rather than the heat exchange servicing.

Cisco,
I'm not sure what's 'sexy' about a few pieces of hose and stop cock, but each to their own.

The purpose of the fresh water flush is to remove the salt water from the heat exchange and the exhaust elbow to reduce the build-up of salt deposits and slow the rust in cast iron elbow.
The fresh water flush does not enter the internal cooling system of the motor only the external.
The internal is cooled with coolant circulating thru the heat exchange.
As there are no andoes on the external cooling system of the motor I'm not sure your comments regarding galvanic action are relevant.

Another advantage of the system is if the leg intake becomes blocked it gives me an alternative method to keep water flowing thru the heat exchange to get home.

FYI the marine mechanic (Ian Coward) is a well respected man who has been in the industry for over 40 years and works out of the Moolooaba marina.