I also have a problem with the valve on the marine head. It leaks and the holding tank empties when the boat is on the trailer. I tried to take it off, but it hits the bottom of the boat when it goes around (i already took the top of the valve off to make it shorter). The only way I can see to remove it is to remove the thru hull and unscrew the thru hull from the valve from below. Is there any other way to do this? What tool do you use to hold the thru hull from rotating. I can see the grooves for some type of tool to hold it in place? -- 73 de AC6KW <mailto:grudin@vdbs.com> Jeff Grudin, DVM Web Add: http://www.vdbs.com/~grudin Ocean Animal Clinic / Cat Clinic of Santa Cruz - Santa Cruz, California Montgomery 23 Hull #072 Norcal QRP * QRP-L * ARS * AR Qrp