Some years back, I acquired a used Dufour 35 with an external strainer installed. The yard I used then was a high quality shop in Marion, MA, and the first thing they hounded me about was removing that external strainer and replacing it with an internal Groco. I did on ocasion, have to open the Groco and clear weed, etc, but very infrequently. Never had to actually rod out the through hull in the following 18 years with that boat.
1985 Marshall 22 catboat