Is there anything that will get the yellow out?

I've tried;
a couple brands of bilge cleaner
Castrol Super Clean
Starbrite Hull Cleaner
Starbrite Black Streak Remover
Boat wash
Salt away
Rust cleaner
Combinations of these
With a scrub brush
and nadda, still a yellow tinge in the lowest area

What's odd is that something cleaned a portion at one time. There are white spots and runs through the yellowing similar to what the hull cleaner does to a yellowed hull.

It's not horrid but it'd be nice if were a bit whiter.

Try some soft scrub with bleach, let set for about half hour (the longer the better) with drain plug in but use no water yet. Just make sure no wires or anything else is in the bilge. Then rinse thoroughly and clean again with some simple green. .02

Greez Off is the best out there, period. If that won't work, some acetone to skim a new surface.

on off bottom cleaner or muratic acid diluted 50/50 with water (read the directions) that should take the yellow right out of any white fiberglass or gelcoat, but it is a VERY strong acid to be working with in a bilge you ideally dont want to get it on anything else and the fumes are brutal, maybe wear a facemask/respirator and do a little at a time.

The best thing I ever used for rust or yellowing was Holt Bowl cleaner. You can get it at Ace Hardware. Just be very careful with it as far as using a brush with it. You get that stuff in your eyes and your screwed. Were gloves and old cloths. I used to use it all the time on my work boats. Its so strong if you get a spot on your jeans you will have a hole there before the job is finished. It will get every bit of the yellowing off though. Just lightly rub it on with a brush. Let it set for about 7 or 8 minutes and rinse it off. Might need to do it twice to be perfect. It will get whiter every time you do it.

I assume you've already found a cleaner but for future reference or anyone else who needs to get the yellow off...pick up some FSR (fiberglass stain remover) from West Marine. It's the best stuff I've used. Let it sit on for a few minutes, and you can literally see the yellow dissolve off. Then just spray down with water and your all set. A little on the expensive side but well worth it.

http://www.westmarine.com/webapp/wcs...5#.Uq90V-Oe_2M