If you can afford it shoot for a system with sequential injection, and if you are going distributor less, sequential coil outputs.
A spark retard, not a spark cut for a rev limiter.
Load it with as much memory as it will hold for data acquisition and set the sample rates as fast as possible...
Sounds like your 540 is really voltage sensitive, at or around 12 volts is it, they will not power up or stay on below that.
Either you have a high compression engine or your battery(s) do not have enough cranking amps or both?
Try a re-wire taking the units directly to the battery(s) or...
Lowrance units need/read .usr files.
I opened your .gpx files and got 141 plot points.
I saved your .gpx files as .usr files for a Lowrance.
Attached is a picture of your furnished .kmz file from Google Earth.
Parker python 2006 - Classic! Went big on a jump and took a nose dive that broke an oil cooler.
Showed up at that race with 2 TT's
Bought and had delivered a huge Weekend Warrior for the wife and kids to stay in because the Blue Water was sold out. Had to buy a Topkick to get it home!