Was it the oil level causing the limp-home, or overheating due to lack of oil? Probably need a computer to read the codes, I know, just wondering if you happened to know.
I should clarify my post: a malfunction in the tilt/trim system will not cause the motor to go into limp-home; it needs to be something that is potentially dangerous to the motor. As far as I know (and this is after a perusal of the owners manual), it boils down to 2 things: temperature and oil pressure. If the gauge was a Yamaha gauge, it should have shown which caused the rev reduction (on my 2005, the fault is shown by a LCD bar under the icon - thermometer for temp, or oil can for oil pressure.)
Not sure, but I don't think there is a low voltage alarm on the motor (electronics just quit at some threshold voltage), and in any case, I doubt that would trigger a limp-home, as that would reduce the motor's output voltage even further. Just a thought.