Water in Bowl
Having recently encountered a similar problem, there are 3 things to check. 1) Make sure the selector is set to dry bowl. 2)Make sure the plunger is all the way down. If left up or partially up, it will allow water from your thru hull intake line into the bowl. 3)Close the thru-hull while sailing if 1+2 don't work. If water is still filling the bowl with the thru-hull open, but the dry bowl set and the plunger down, then you may have to replace the seals located inside the plunger assembly, as is my case. A head rebuild kit may or may not work. You didn't mention what type of head you have, but the Groco model does have an upgrade kit at WM for $134 vs. $299 for a full new head. Rebuild kits cost around $60-$70. Good luck and let us know how things turn out.