Water out of manifold bolt holes?
 

The six-year-old hot exhaust section on my A-4 corroded out. It was black iron. The engine is raw (salt) water cooled, and I put about 100 hours on the engine every year. Every time I put the boat away I flush the raw water out of the engine with fresh water.

As I removed the exhaust section, water trickled out of the two manifold bolt holes that mount the flange. The dry exhaust part of the manifold was dry, however.

Is this normal, or is the water cooled part of the manifold corroding, allowing water to seep to the bolt holes? The manifold is about 10 years old. Before I started working on the engine a mechanic replaced the original manifold with an aftermarket one.

Thanks,
Chris

On the original manifolds, I think those holes were blind (ie: didn't go through into the water jacket). Aftermarket manifolds may be tapped through. Big issue as I see it is exposure of the fasteners to water and the resulting corrosion.
Recommend you change the fastening configuration for your exhaust flange to studs and nuts. I'd make stainless studs out of set screws or all-thread and bond them into the manifold with JB Weld. Then use nuts to hold the flange to the manifold.

Thanks for the reply and recommendations.