With respect to sight tubes on Diesel tanks: I wouldn't be without them. My electric gauges show empty when the tanks reach one half full, a nice conservative measure. But, I want to know my exact level for cruising safety and refill estimates. However, my plastic tubes, which run from the bottom of the tanks to the top, have a positive shutoff lever, which would prevent any loss of oil, save the contents of the tube, in the event of complete removal. On the plastic tube, I have a wire tie, which I slide up and down to monitor the fuel level and consumption much more precisely than does the electric gauges. Capt. Howard W. Evirs, Jr. M/V White Squall Sea Ranger 46