I have done 2 enduros with no watch and no odometer. I just wanted to finish. Say you are on line 60. You start one hour after the first row. When it is your turn you go as fast as you feel comfortable. When you hear a loud 4 stroke revving behind you pull over, let him pass then carry on. Make note of the row numbers of the guys passing you. If you are number 60 and you are passing up to row 50 your are too fast. If you are 60 and everyone is passing you, you are slow. If you are hanging with row 59 and they have fancy enduro computers and ride well you are close to on time.
If you come around a corner and see 4-5 bikes waist deep in mud, stop and find a route around the mud hole. Thank those 4-5 guys for marking the mud hole.
Don't go too fast. I got passed by a fast guy who appeared competent. I got passed by him a bunch of times because he would crash or hit a tree shortly after passing me. This happened a lot. I would let them by and they would crash.
ICO Racing Checkmate Enduro Computer
All that timing stuff is great, but if you have to go faster than your capabilities to be on time then what is the point. Enduros are a blast and make you a better all around rider.