Looks like 3m BoatBlue. Same as I did mine. It looks great but i find it not very durable. Dont get too mad when you need to put patches on....ITS GONNA HAPPEN!
You still didnt say what drives you have on the boat.
For sterndrive you would want this: (plus whatever AP system you want, probably should go with garmin. No reason you should be anymore than $3k if you install yourself)
Octopus Sterndrive System F/Mercruiser From 1994 & North American...
As far as the battery drain if you dont turn off the batteries, just wire your NMEA2000 backbone to a switch. I believe if the backbone is tied directly to the battery all devices powered via NMEA2000 will stay on all the time.
What kind of MFD do you have? What type of drive?
Typically it is best to get the same brand AP as your MFD/Chartplotter. For sterndrives, you would get an Octopus drive unit.
I had a great experience with Lightstream. I originally did a balloon loan with my bank for my boat, after the allotted term the bank wanted me to refinance and the rate would have been like 11% because of the age of the boat.
I ended up getting a loan from LS for like $10K, funds were in my...
Draining ALL the water from the block and leaving it empty will work 100% of the time. As far as rust goes, remember your block sits with lake water in it for the entire summer, there are no rust inhibitors in lake water so whats the big deal with air in the block over the winter.
If thats really all you can find then you have 2 options.
Use it and then drain your motors in the spring and recollect it.
or
Drain the water out of the engines and leave them empty, no antifreeze. Thats what I do