What was found
PILOT ABORTED TAKEOFF OUT OF TEB WHEN THE RIGHT ENGINE LOST 400 RPM. RETURNED TO RAMP, TRIED A HIGH POWER GROUND RUN, AFTER 10 SECONDS THE ENGINE STARTED SURGING AGAIN. MAINT FOUND WATER IN THE RIGHT WING SUMP. DRAINED WATER, CHECKED FILTERS, CHANGED FUEL CAP O-RINGS, NOW OK FOR SERVICE.