44 MY transom core question

So while poking around in my new to me 1988 44 MY I discovered something very disturbing. When I pull out the drawer on the port side next to the bed in the aft cabin I can see evidence (weeping from screw holes, hollow sound when tapping) of about a one square foot area of rotted transom core centered on the area where the trim tab pump is screwed to the transom. The odd thing is that this area is below the water line. The two trim tab hoses also appear to be installed through the core when looking at the inside of the transom, but looking at the outside shown in this photo they clearly exit the hull well below the water line. And the chine step shown in the photo is not visible from the inside, no obvious step-in on the inside of the transom. From the inside the core appears to go right over this chine step without a change in profile. From the inside looks like the core terminates exactly at the level where the lower trim tab hose goes through the transom, but this is clearly well below the water line. I had to leave the boat before I has a chance to investigate thoroughly but when I got home I looked at this photo and something doesn't add up. I'm wondering if the area that appears rotted is not the core, but is a piece of wood glassed to the back of the transom to allow mounting of various things, so not structural. From the photo I would assume that the core terminates at the chine or somewhere above the chine. It would seem difficult and pointless to continue the core below the chine during manufacturing. If it goes below the chine then it also goes below the waterline, which I didn't think was supposed to the the case with these Vikings. Does anyone know if the core in the transom terminates above the waterline. If this is the case then I think I'm okay.

Thanks for the core photo. I believe the water entered my core through the penetration for the upper trim tab hose, but not quite sure yet. Still investigating. Could have possible come from the rub rail, but the glass rings like a bell above the trim tab hoses and all the way up to the rail, dull thump below the upper trim tab hose. The lower trim tab hose appears to be below the core. It’s a mystery why Viking would have installed the upper hoses through the core when they easily could have moved them down a few inches to be in the solid hull. I’ll also take a closer look at my spare shaft cap. The cap is on the side with the wet core. It appear the have good core when I looked, but I’ll check again and seal the core under the cap.