Last week, I was doing routine engine checks on the Universal M25xpb diesel on my 2003 Catalina 310. I noticed a slight drip from the port side end cap of the 18 year old heat exchanger. I tightened the 3/8 diameter brass bolt and it snapped right off. I removed the heat exchanger, and took it home in an attempt to drill out the bolt. I ended up replacing the unit, as it looked severely corroded on the inside. The aftermarket Seakamp unit, like the original is bronze, or some other copper-tin alloy. So are the bolts holding the end caps in place. I am contemplating replacing them with much stronger stainless steel. Would the benefits of having stronger bolts outweigh the disadvantages of galvanic corrosion between dissimilar metals? To reduce this effect, I am considering using an anti seize compound on the threadss I also though of draining the seawater via the petcock after each use. Any thoughts or feedback, please respond.