Your raw water strainer may not necessarily be bad. Green is simply a sulfate compound that forms on the surface and is not really a sign of corrosion. And strainers usually have heavy walls that would take a lot of corroision to do them in. Inpect yours, but I suspect it is ok.

So you can only get to your speedo paddle underwater? Someone makes a flexible bottom paint for it. I have a bottle in my boat junk bags but never used it. Also maybe you can reach it from the dock with a long handled brush and give it a scrub. That is kind of hit and miss however.

David