I have a 05 33 Outlaw with 496 HO's (70 hrs on engines). It has been in the shop numerous times for the starboard engine going into guardian mode when running in rough water trimmed out some and at speeds above 60 mph. The problem never occurs as long as I am running in smooth water. It is not the rev limitor. This last time Marine Max Clear Lake said they had finally found problem ( water pressure sensor). Same problem again a week later while running in rough water. Back to the shop again. They put it in the water again yesterday and made numerous passes in smooth water and found no problems (had lap top plugged in to collect data). They then had to make only one pass in rough water for alarm and guardian mode to cut in. They say low pressure points appeared on readout. The water pressure sensor had been replaced the week before as they thought that was the problem. Now they want to change out the impeller. There has never been an overheating problem. Any ideas or suggestions before I go and replace something else that might or might not correct this problem

I would go ahead and change all the sensors from the other engine into this and vise versa.
If then the other engine has the problem ,,its the sensors,,if not its something else.
I hate electric stuff on marine engines,,and this is the reason why.

I would imagine that in rough water the drives are coming out of the water, or high enough to get the pick ups out of the water? Is it possible that pressure falls at these points enough to trigger the sensors?

Swap the sea pump assy's around,
and see if it acts up over there.....if it does,
you know it's a problem with that piece.