[C320-list] Heat exchanger core and mixing elbow

[dprudden at comcast.net]

I have a friend who has the same engine as me (and a lot of you), a 3gm30f. He works for a very reputable (and expensive) boat yard in Massachusetts. He says, and his yard agrees, that the mixing elbow should be replaced every 5 years and the heat exchanger core should be pulled and sent out to be properly descaled/cleaned every 5 years as preventative maintenance. I know there was a recent discussion about cleaning out the mixing elbow, and this is obviously more than that. Agree or disagree????? I sail in salt water. Does the number of hours used each year matter? 

Thanks for the help and advice! 

David Prudden 
#787