89 mid cabin thru hull clog

[mrrudely]

these are photos of the fittings immediately after the thru hull for my generator (taken yesterday)
water flow was all but completely restricted
I discovered the same thing almost three years ago when we first bought the boat
the boat was sitting for many years and the generator almost certainly wasn't run for more that 5 years
I cleaned the fittings, put things back together and have been starting the generator regularly ever since
yesterday I discovered the fittings were clogged up again
the thru hull itself is clean, just these fitting were clogged
I am replacing the fittings (with one piece instead of the two)
so the question is
is this normal? or is something going on?
do I need to worry about the engine thru hulls?

[prowlersfish]

Looks like you get a lot of growth in your area. It's possible the engine thru-hulls could have issues too. Also your heat exchangers and oil/trans cooler(s) Rydlyme marine and Barnacle buster work well.