How does a boat get so nasty just sitting under a shed? Cleaned our's up today, lots of simple green and pressure washer

Same here......................had to add a little bleach to the mix on mine. Seats and cushions had the mildew funk. Even turned the key and ran her a few minutes.
Now, if I can only use her before the dirt and mildew re-appear.

That's not dirt and mildew!
It's boat pout.


Ever notice how happy a boat seems to be after a day on the water.
Just washing it up makes it feel better.













Mine's gots the same problem.

Oh, after the Simple Green, bleach, pressure washing, etc, you have now severely cleaned the surfaces, they are now even more subject to staining and such.
Finish off with a wash and wax, even the cheap stuff will work. Makes cleaning off blood and marsh scum a lot easier.

SLOWLY waxing it today..............uuuuhhhhhhhhh

Try Woody Wax. It only takes like 6 squirts to do all the non-skid. I know it cost quite a bit but one can should last a long time. Make sure to follow the directions