Twin 350s raw water cooled. Never gets over 125 degrees. Cruising at 2400 rpm 10 miles out. Port engine drops 400 rpm smells hot. Open hatch left side viewed from above smoking between the head and manifold shut down. Hot metal sound and boiling water sound. Right side of engine pretty normal. Slow to restart idled to circulate water. Then shut it down to come home. That manifold and elbow new as of last year