Did Hornblower cheat?

Hi, I'm new to this forum, and I only registered to ask this question which has puzzled me a little.
It's been a while since I read Midshipman Hornblower, but watched the series recently. Hornblower joined the Navy at 17, but he became a lieutenant fairly quickly. IIRC, the rules for promotion was that you had pass the examination, which you had to be 19 years old to stand for. You also had to have served a minimum of 6 years at sea. I don't think you needed 6 years as a midshipman, but still, you would have to serve 6 years before you could present yourself to an examination board.
This means that if Hornblower played by the rules, he could become a lieutenant at 23 at the earliest. Now, I got the impression that Captain Keane knew Hornblower's father rather well, and that was the reason Horatio was given a place on his ship. You had to have the connections to get your foot in the door back then, even if later promotion came from merit. From Patrick O'Brien's books, I understand that it was not unusual to have children of friends and relatives registered on the ship's books, even if they were still home and at school. This was illegal, but done anyway. Since Hornblower obviously didn't serve 6 years at sea before becoming a lieutenant, did Hornblower's father make a deal with Captain Keane to have Horatio on illegally on the ships books while Horatio was still at school?

Did Hornblower cheat? Of course he did, just like any one else who had the connections to have a captain put his son's name on the books of a ship before the youngster actually made an appearance on board. This 'book time' was a widespread practice, and unofficially condoned by the Admiralty in the interests of keeping the community of prospective naval officers and their families happy. It enabled those who benefited to get a leg up in the scramble for seniority towards that all-important promotion to post captain.

The rules said the prospective lieutenant must have 6 years at sea, have reached the rank of midshipman or master's mate, and be at least 19 years old to be eligible for the examination for lieutenant. Since Hornblower was 17 when he entered the navy in 1794, he would have needed book time to show six years at sea when he was promoted to lieutenant in 1797, when he was 21. Surprisingly, Parkinson in his 'biography' doesn't mention this issue, an uncharacteristic oversight by a very fine historian.