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Every flange and joint in my boat has fine white crystals growing

Hey all, while this isn't specific to my twin screamin' jimmies, this is the second powerboat I've owned that has shown this - my 3 sailboats never. And it's getting worse.

Like I say in my topic line, every single joint and flange in contact with saltwater is growing white fluffy crystals. I've tasted it and it's alkaline and NOT salt. Everything from stuffing box mounting bolts to cooling line connections anywhere on the engines and water intakes/through hull valves. Even on valves for the heads. Any joint in contact with salt water.

The strange part is that I can't find ANYTHING on the internet that mentions this, yet I had the same issue with a '57 woody runabout I had.
All my zincs - external and internal are up-to-date.

I could just vacuum the stuff off - it's extremely fine and delicate, but I want to know what it is. None of my sailboats showed this stuff anywhere.
 
Probably galvanic corrosion with the salt water acting as the electrolyte. Your zincs need to be in contact will all the metal in your salt water system. For example, the engines should have zincs in the exchanger and salt water pump, but if those zincs don't have a metal to metal path to all parts of the system you can get galvanic corrosion. Sections separated by hose connections aren't protected. Joints connecting dissimilar metals usually show the corrosion first. A ground wire may need to be installed between protected metal and those isolated sections.
My current boat (twin DDs) came with large cast iron, dual strainers. When I checked the baskets, there were no baskets. The old owner told me they kept corroding away and gave up. The strainers were separated by hose from the sea cocks and engine. Running a copper wire to bridge the hoses solved the problem.
 
I never thought about that. For some reason the bulky cooling system on these are several metal sections isolated by several short sections of hose. I've got 3 engine zincs I believe, and that sure doesn't cover all the bits and pieces.
 
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