2004 F225TXRC Speed indication

[Drawplus]

Is there a diagram that shows the the speed system, components & locations. With twin engines how to tell which is sending info to electronic speedometer? Got into sand and now speed indication is not working. I back flushed and the port that I think is the pick up port had water flowing from it.

[rodbolt17]

typically the left hand rotation engine is plugged and speed is taken off the right hand turn engine.
either one can be used to supply water pressure to the speedo.
its a simple plastic tube.