u/Total-Pudding

Here's a video of the water coming in

I took the boat out into the water, but before I could do anything, I heard water coming in from somewhere, I narrowed it down to what I think is the driveshaft bellow? Is that what this is, or is it something else that's causing it?

I got a mercruiser 3.7 i just got the boat finished and ready to take it out on the water for the first time, previous owner winterized it. Do i fill the riser completely to the cap with coolant? Before running it in the lake? Is this where the coolant fills up at?