Water in Sailfish

Search on here (and the net) for more info, but most likely the reason you are seeing this is because (as is typical with Grady's), the stern bilge is actually higher than the mid bilge. Meaning, water will first collect in the mid bilge - if there's enough, it will then run towards the stern bilge. Once the boat is positioned with the bow high, water will then run back to the stern.

The question, of course, is "why" are you getting water in there to start with? We'll need more info on that from you in terms of how you are using the boat and accessories/options (livewell/fish boxes/etc) along with when the last time you resealed all of your thru-hulls and deck hatches/plates. And, during your outings, does your cockpit floor get wet or does it stay dry?

I've been chasing this on my boat. It only happens when it's choppy. I suspect it is water coming back in through the rear bilge line from the boat rocking in the chop. Another member here with a newer Sailfish experienced this problem one time when navigating the great loop. Turns out that one time was in Lake Erie when it was choppy. My rear bilge discharge is a straight drop from the thru hull. One of these days I will tape it over to see if it stops or add a loop that goes up higher to prevent the backwash.

A couple of thoughts on the matter here.... first would be do you pull the boat out of the water every time you're done for the day or do you have it wet slipped somewhere? When you do pull the boat out, do you pull the drain plug out of the boat and leave it out until you get back home? I ask because if you have it wet slipped or stored somewhere for a considerable period of time to where when it rains, you can have a fair amount of water seep into the bilge, especially if you get a good amount of rain. Going along with that seeping into the bilge comment that I just made, I'd check the circular deck/pie plates, make sure none of them are cracked, damaged, missing their rubber seals and so forth, as you can get a surprising amount of water seeping through them into the bilge if they're damaged, etc. Especially if you're in rough conditions and taking waves/water/spray over the front or side and into the cockpit of the boat. The screw in deck/pie plates are also a good idea to convert them over, if you haven't done so already, as the other ones can pop out quite easily, and again if they're the original ones for the boat, they're almost 30 years old now. As mentioned above, I always pull the drain plug at the ramp if possible and then leave it out, go up and down several hills and then go back to my beach cabin when I take the boat off our mooring buoy at the end of the season. The reason for this is that I've heard several Grady White models, and I imagine even other boat manufacturers out there as well, have oddly shaped bilge areas to where it's possible that you won't get all of the water out of it if you're driving flat/level roads all the way back. Of which if you're not doing that every time and aren't getting the water out from the previous trip, you could still have water in there from the last time and think it's from your current outing. As you mentioned, check the bottom of the hull as well as all of the thru hulls, check your rubber scupper flappers, live well, hoses, other intakes/drains coming into and out of the boat, and make sure none of them are leaking. How much water are we talking about here, a gallon or two, or considerably more than that? Good luck!

I would be surprised if that is where the water is getting in.
Assuming the chop is not washing over the deck, I would look at the deck mold to hull mold seam under the rub rail. Not all that easy to do.

One test that might help is to use a hose to really soak the deck and everything on it. If you don't get water in the bilges but do at sea in chop, the seam may be the culprit