I to did Gen Nav in 2005, failed it the first time, passed the second time around
with 20 min to spare at the end! What I found worked for me is I did the exam in order, if I was on a question for to long I would skip it and come back to it.
I used Bristol GS Question Bank and Forum. If you don't understand a question,
write it down step by step how to get the answer, don't memorize the QB answers! Keep practicing Bristol GS QB.