I know we never had them serviced and the previous owner did not appear to abuse the boat but at the same time did not appear to bother any of the boat mechanics in Buffalo very often. I doubt he ever had them serviced eiher.

I am waiting to hear from the broker and mechanic #2 who is supposed to be the local Yanmar expert in our area.

I doubt that it is a blockage of the elbow. I had it apart last summer to replace the riser pipe that had rotted through and it looked clear to me. Remember we are fresh water here.