OpenMarine

Didn't really expect that, my Pi3 never ever gets turned off. living on the hook opencpn is always running & recording a track. Always on & never crashes. So just moved across the bay to hide from some higher winds tonight & noticed the Pi was rebooting. Data recorded to presumably to time of the crash which showed the anchor windlass was finished doing it's work, nothing obvious electrically. 
So where can I look to get maybe shed some light on the reason? 
I never really pay much attention to the logs, there are a load in /var/log
pi@openplotter:/var/log $ ls -la | grep log
-rw-r-----  1 root    adm                13926 Feb 18 14:40 auth.log
-rw-r-----  1 root    adm                  8830 Feb 17 23:52 auth.log.1
-rw-------  1 root    root                7329 Feb 18 11:17 boot.log
-rw-------  1 root    root                7473 Feb 18 00:00 boot.log.1
-rw-r-----  1 root    adm            142992701 Feb 18 14:41 daemon.log
-rw-r-----  1 root    adm              26540353 Feb 18 00:00 daemon.log.1
-rw-r--r--  1 root    root                2952 Sep 21 10:00 faillog
-rw-r-----  1 root    adm                47423 Feb 18 12:54 kern.log
-rw-r-----  1 root    adm                47750 Feb 17 21:30 kern.log.1
-rw-rw-r--  1 root    utmp              292292 Feb 18 14:38 lastlog
-rw-r-----  1 root    adm            143054171 Feb 18 14:41 syslog
-rw-r-----  1 root    adm              26598233 Feb 18 00:00 syslog.1
-rw-r-----  1 root    adm                10523 Feb 18 13:39 user.log
-rw-r-----  1 root    adm                  9516 Feb 17 22:10 user.log.1
-rw-r--r--  1 root    root                21847 Feb 18 13:39 vncserver-x11.log
-rw-r--r--  1 root    root                20996 Feb 18 08:55 vncserver-x11.log.bak
-rw-r--r--  1 root    root

Any pointers to speed up hunting this down?
Thnx

My first openplotter used to crash.
It was on a Pi4b with 1Gb , mainly when panning maps. Since getting a Pi 4b with 4Gb I've had no more crashes.
Dunno.. just my experience.
Cheers!