Mystery solved
We found that while under hard sail on a port tack, lake water was coming in from somewhere in the stern and pooling on the starboard cabin sole. While under power, there was barely any water coming in. After spending time in the aft starboard locker (try it sometime ....I am 6"2" and 250) while under sail and in port at our slip, we found with the help of mirrors and lots of light, a tiny hairline crack on the "backside" of the Yanmar 3" water exhaust hose about 1" above the hose clamps. After finally removing the hose ...whew... we found that the wire reinforcement inside the rubber hose had rusted enough to subject the rubber hose to a thin wall + hairline rubber crack. While sailing under 6-7 knots hull speed while heeled over on a port tack, the back pressure from the lake water forced the water back up through the crack and squeezed out of the hose into our vessel! There was enough hose to allow us to cut and remove the failed hose section -4" and reattach - also using some 3m sealant adhesive on the nipple. Hopefully the pictures attached give some clarity. Thanks everyone for responding with suggestions of where to look. A long process!