2 stroke engine, model ICCXCOM on OMC sea drive, 1987, 400hrs on clock, runs 10 minutes then cuts out for 1 sec, votmeter drops off scale, then engine recovers. Repeats every 15 minutes for first hour then runs OK.. ..but last trip stalled after 1 hour in rough conditions. Re-started in neutral, revs sluggishly, in gear revs to 2000 rpm then dies. After 2 hours & several restarts with same result, started and ran OK. By then, in calm conditions. One of the two parallel 12V batteries tested low capacity. Oil consumption seems higher than manual suggests.