Re: On a Merc 470 heat exchanger....
One note of caution here, is that you need to make sure that the gasket makes a good internal seal. The raw water flows through the exchanger tubes several times. The tubes are grouped in bundles, some flow back, some flow forward. If you do not have a good seal on the solid internal ribs that isolate the groups of tubes you can get "crossover" and the flow can be reduced in some of the tubes. If the endcaps or gaskets are in poor shape this could reduce the efficiency of the exchanger, and we do not want that.
