Other mistake: Rick mentions "It'll take us half the night to limp home and I don't want to go through the reef in the dark with one engine." He's lying because he wants to spend the night with her, but even considering that, the fact that there are islands behind him as he speaks, but through all the rest of the scene both act as if they were in the middle of the ocean (she does not object, he looks out to sea with his binoculars), is a spoiler. (00:30:30)
Other mistake: Magnum is 5 years old when his dad leaves for Korea, and is 6 by the time he's dead, coming back in a coffin on July 4th 1951. That does not work with the birthdate that appeared on the driver license in Memories Are Forever, episode 2-5, which is even abundantly referenced here with footage being re-used (Magnum's wedding party with bombs, and making love to his wife years later in the guest house). He was born January 5th 1946 in the document shown in close-up there.
Other mistake: Rick breaks off his hot date and goes searching for Magnum driving his boat for a long while -before- contacting Higgins to see if Magnum is missing at all. It also is the middle of the night and close to dawn (Magnum has to wait just one hour before the sun comes up) but Rick is still drinking wine (but not drunk) and hasn't even touched second base with the girl despite the fact that they were mixing wine and going below when the sun was still up.
Other mistake: Higgins says he hasn't seen Magnum (or his surf ski) "for two days", but Magnum left on the morning of the 4th, and has been in the ocean for 20 hours total. He spends the 4th on his own, but on the 3rd his friends and the ever-seeing majordomo of the estate should have gotten any sign of his presence.
