You're sailing in FRESH water
The density of fresh water is less than that of salt water. The draft of most boats is rated as for salt water. AS a result, your draft is deeper than advertised.In addition, once the 310 was built, Catalina used the same keel on both. The C-310 has less draft than the older C-320s, so the current advertised draft for the C-320 is 4' 3" while the older ones were advertised as 4' 8".The draft of the fin keel C-320s changed too. In 2002, the advertised draft was 6' 5.5" and the current draft is 6' 3"SteveAlchemist #909 (fin keel)Holland MI