I HAVE A YAMAHA 250 WITH WATER PRESSURE PROBLEMS. WHEN I AM RUNNING 17-18 LBS. PRESSURE I AM GOOD TO GO BUT IF I BUILD MY PRESSURE TO 20 LBS. IT WILL SLOWLY START FALLING TO APPX. 5 LBS I HAVE TO STOP AND START OVER AGAIN. NOT OVERTRIMMING OR BLOWING OUT.ANY IDEA?