The only small challenge when switching from a relay to an ACR, is the ACR will be active anytime the start battery voltage is above the ACR activation voltage. So if you have separate shore power chargers for the start and house bank, that will be defeated, as the start batt charger current will now flow into the house batt.
If you are making no other changes to the vessel electrical system, I'd stick with a relay.
Assuming you have the stock alternator, a 100 Amp CONTINUOUS DUTY solenoid relay should be plenty. Cost will be around USD60.
Another option is the BEP DVSR. You cut the short red wire and use the ignition 12V that you already have at the solenoid to activate the ACR (DVSR) only when the ignition is active.