My 1984 m25 has a raw water filter located on the bulk head starboard side a little higher than the pump on the engine. That said , my problem is every spring the pump loses its prime and I spend time filling the system. Is the filter in the correct spot? After looking at other C-36s I don't always see a filter in that spot. Why does it lose prime?
On my 1988 boat the water strainer/filter is right at the though hull attached to the seacock. I have not had any problems but my boat stays in the water year round, I do shut the seacock off when I leave the boat. Having your filter so much higher than the water line I am sure inhibits the pumps ability to self prime. The raw water pump it self is very near the water line if the lines and filter are below that level the pump has a much better chance of self priming. Even with the seacock off I bet it dribbles enough to empty the line to the filter when the boat is on the hard. The raw water pump does not suck air well or for long.
Cepheus dream
C36 MK I # 825
MK I Tech Editor No Mas