I had an additional A/C unit installed, but I did the sea strainer installation using an existing through-hull fairly high in the forward 1/3 of the hull. It was difficult to get the top of the sea strainer AND pump below sea level because of the height of the through-hull, the angle of the hull, and the narrow space available. The pump was barely underwater with the vessel fueled and at rest and was certainly going to be above the underway waterline. Initially, all was well, but eventually I started loosing prime while underway. My theory was that as the hull lifted out of the water at normal cruising speed of 8-plus knots at 1600 RPM on both engines, the centrifugal pump in the system, which was now above the waterline, lost prime. I installed a scoop type external grating over the intake to ensure that forward motion of the boat kept head pressure on the strainer and pump, but occasionally, I still lost prime. The final solution was found when I carefully observed the clear hose between strainer and pump and saw a bubble form along the top of the hose. I had been certain that I had a steady uphill climb from through-hull to pump, but it is not always easy to tell whether that aim is achieved in the confines of the engine room. No bubble had shown up during installation and testing, but apparently enough air got swept under the hull in time to collect in this two foot-long section of hose and cause the pump problems. Moving the sea strainer one inch downward permanently cleared up the problem with any bubbles ingested while underway now swept through the entire cooling system. Rich Gano CALYPSO (GB-42 #295) Southport, FL