The exhaust of a Jet Ski is a casting with an inner pipe and an outer pipe. The exhaust goes through the inner pipe and water goes between the inner and outer pipe. During the casting process a sand core is necessary to form the cavity between the inner and outer pipes. The casting is designed with holes on the outside to support the core and to drain the core sand. After the casting is complete caps are welded on to cover the holes. The material of the caps is more susceptible to corrosion than the casting, so they act as a sacrificial anode and corrode first. Attached are some pictures of the process that I used to replace the caps on two exhaust manifolds.
1. Manifold with damaged cap

2. Close up of damaged cap

3. Damaged cap ground off

4. Paint ground off

5. making new cap

1. Manifold with damaged cap
2. Close up of damaged cap
3. Damaged cap ground off
4. Paint ground off
5. making new cap
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