Ohhh sh#$%@^%$
All fine advice from previous posts, but they haven't seen what you have. Henry, I've done it on my 1990 H28 and it was NOT easy to due to:1) impossible location (under stern step and behind rudder post)2) poor aluminum original fabrication (absolutely replace with plastic)3) limited access to remove old tank and place new one.I wrote a brief discussion several months ago on this about my experience. You might check it out the archives. PS If you're the same Prof. Henry Milam from Drake email me and I'll share the inside details. Good luck!