Is this the end of my V20?

[cfelton]

Sounds like you either have a leak in your manifold or the riser/resevior . You can buy the riser from Mercury Parts Express but you may have to buy a used manifold. If you look up into the exhaust (round ) end of the riser you may see globs of rust and scaley rust. Take a screwdriver and pick around ta see if you can pick a hole into the water jacket. If your manifold is aluminum the riser/ resevior will be cast iron. Some are the other way around. Theres a place nearby called Budget Boats in Va. that has tons of good used parts for these motors. It sounds like your riser blew through. If the riser is bad buy a NEW one, not used!