A year ago I helped bring a 90' Custom twin screw (1500 hp, 3000 total) boat over from Hong Kong. We ran one engine at a time, alternating about every 6 hours at about 14 gals an hour and 9 knots at about 1400 rpm. We carried about 5500 gals and the longest leg was about 3000 miles. We had a generator running and I estimate it burned about 2 1/2 gals per hour. In other words, 16 1/2 gals per hour to cover 9 miles, or 350 hours to run the longest leg. My recollection of the longest leg length may be a bit high. If we had run the other engine it would have added at least 2 gals per hour to the burn. Running it at idle would have been very bad. Running both engines in tandem at same rpm and 9 knots would have had them running so slow that it would have been hard on them. These were high speed turboed engines. This describes the problem in general, but of course it may not apply as well to 2 much smaller engines. The general principles are the same. Mike _____________________________________ Capt. Mike Maurice Beaverton Oregon(Near Portland)