Re: 90 HP Evinrude E-Tec
Seahorse is quite correct. W/O the sw and other diagnostic tools, you don't have a chance. I don't think they sell the version I have any more, but I already had a Palm OS device and the sw I have runs in the PDA, which is very small and compact and it dumps all the diagnostic data collected to a PC when synced. You can also read the data in the PDA, albeit, small chunks at a time. If you find the sw is still available, let me know and I will tell you exactly what interface cables (2 are needed) to get.
BTW, if memory serves me right, the cables and sw ran ~ $200 and the shop manual another $65 or so.