Maybe you could fill the ballast tank, either by launching or by hose (240 gallons!?!), then letting it sit on the trailer to see if any water seeps out that crack.
But don’t drive any distance or speed that way.
good idea... maybe add some dye to make it easy to see.
Best case senario the crack does not go all the way through and you only have to do the outside job. Grind and feather out the damaged glass and put a few layers in. Worse case senario you are looking at a long weekend of repairs. If the crack goes through, you will want to put a "backing" plate of two or three layers of wetted fiberglass matt on the back side of the crack. There are at least two ways of getting a backing plate inside your ballast tank the first requires that you cut an access port (there is another way-- see below). So probably one of those 6" access plates..(8" would be better) to get inside the tank. Once you have the backing plate done... gently grind out and feather the crack from the front and lay in a few layers to get it fair again. There are a few tricks for doing that easy and fast also.
After you have feathered out the cracked area from the outside you will want to make two or three layers of overlaping pieces of wetted cloth. When making the feather'd layers for the outside job... get a pice of plastic sheeting from Lowes or HD and cut out a piece that overlaps the job area. Lay it over the area and trace the shape onto the plastic sheeting using a sharpie. Use that as a template to cut out the first piece of fiberglass cloth. Then cut about three more pieces of cloth each a little smaller than the previous.
Next cut out another piece of plastic sheeting that overlaps the job by about 4" and overlap masking tape around the edges. Wet each piece of fiberglass cloth with epoxy resin and stack them largest to smallest on your plastic sheet. Squeege out the excess resin and take the plastic sheet over to the job and tape it to the hull taking care to line up the pieces of cloth with the faired area. Let the resin set. The plastic sheet will do a good job of creating a smooth job but you will need to do a little sanding, fairing and then barrier coat the area before painting. You will never be able to tell it was cracked.
There is an alternative way to making a backing plate that does not involve cutting an access port. I have done it once before but not on my Hunter. I can walk you through it but it is rather long for a post. I posted some pics to give you an idea of how the job is done without the cutting of the access port...
If you need guidance on the making the port or the fiberglass steps, start another post or PM me. There are a lot of us here who have done these jobs.
