The alternator output and glow plug mods are very worthwhile changes. Do pay heed to Mainesails' comment:
"Please note that I generally advise running the alternator output directly to the house bank, not to the starter as shown here. You can then install an automatic combining relay (ACR) or an Echo Charger between the banks to charge both simultaneously. Doing this will remove the potential for fried diodes via the flipping of the battery switch through the OFF position."
In the meantime or if not going to install the ACR, try to not rotate the battery switch while the engine is running. Each time you do hits those diodes with the alternator output and even though they were rated for it when new, they just aren't that new anymore.
I'd encourage doing the glow plug mod as well, because it is also running a high current 10 AWG circuit through those 35 year old (in my case) corroded trailer connectors. When replacing the trailer connectors with terminal strips, the one near the starter is easy to find and replace, but don't forget that there is a second trailer connector hiding beneath the cockpit control panel.
fwiw - I made up some combined schematics a while ago (example below) and have been finding that the diagrams they were based in differ from how the boat was wired. Most of what I'm seeing does appear to be the 1985 factory wiring so I can't blame previous owners for most of these and the message is to check yours before making electrical changes. When I finish the current fuel system replacement and can get in there with the schematics illustrationon the iPad I will update the electrical schematics and post them.
Sure thanks my email is email@example.comPM me your email and I'll send you a pdf. There've been some updates since the version shown.