There are dozens of ways to wire up a system in a boat.
In general, in a vehicle, the voltage regulator is not going to allow the mid 14's to be held for long enough to quickly or fully charge the engine battery, much less the house battery tacked onto the end of that weak underwired circuit.
Overcharging/charging too fast is not an issue, as long as the voltage regulator has not turned psychotic.
An alternator only makes as much amperage as is required to maintain the voltage the voltage regulator allows,
The battery health and state of charge dictates how much current is required to maintain that voltage.
Voltage drop along the circuit from alternator to house bank is the issue affecting most. Too long, too thin and too little voltage makes it to house battery, meaning too little current and too little recharging occurs.
A fat copper circuit between alternator and house battery will allow the battery to feed properly when depleted, but at the cost of alternator life.
For Me an Alternator swap takes 15 minutes, and my lifetime warrantied alternator was free, when I replaced it after 9 years of regularly maxing it out with depleted batteries and a thick circuit.
Voltage regulators in vehicles might be external or internal to the alternator. The internally regulated alternator might have a voltage sense wire that carries no load and allows finer adjustment of output voltage to counteract voltage drop on the circuit.
Usually VR's are too timid, and drop down to the mid to high 13 range well before a depleted battery would like. The manufacturer was more concerned about not overcharging a battery than it was about properly charging a battery for maximum battery lifespan.
Mine allows 14.9v, which is a bit high, but then it drop to 13.7 prematurely, and sometimes a 14.1v will be the max target voltage. I've no idea what the triggers are for it to choose one of these 3 end voltages. My VR is in my engine computer, and I've given up on the idea of influencing its behavior to Kowtow to my desires.
There is a 'Trickle charge' mindset alive and well carried over from grandpa's astounding knowledge of batteries, that a slow recharge is always best and is required, that anything faster will warp the battery plates and boil off the electrolyte and kill the battery.
This theory belongs locked up with the old wives and their crazy tales.
When one is heavily cycling their batteries the best thing one can do for the battery is recharge it as full as possible as quickly as possible, as long as the voltage is not allowed over 15v. The battery will decide how much current to accept. The dangers are only if the battery is already extremely hot at 110F or more and voltages are allowed to go too high. This can do what grandpa feared, but normal battery temps and mid 14 voltages is not an issue.
Sterling makes DC to DC converters to properly take whatever output the alternator makes and refine voltages into 3 stage charging. Their main advantage is maintaining high enough voltages for long enough to fully charge a battery via alternator. Rarely is the opposite a concern, trying to tame an voltage regulator/alternator into not allowing it to overcharge.
If one puts a digital voltmeter on their dashboard, that measures house battery voltage at the house battery terminals, one will usually be surprised how low that voltage is with the battery depleted and the engine running.
