Emergency generator??

Worst case is you need to start your emergency bilge pump and all that happens is the genset grinds to an immediate halt. The inrush current on that inductive load is many times the FLA rating.

You're left with a dead ship whilst potentially sinking.

His system is set up to be USCG Subchapter T compliant. This is required for commercial operation but also used when a builder/operator is looking for best practice guidance.

For personal/recreational use there are no required standards in the US, not even something like the European RCD. If this is the case, he's free to change what he has but should understand his existing system before making modifications imho.

OP's questions were why his system was set up the way it is and were there potential down sides to changing it. I'd say those questions were answered.

Relevance to a particular spec is for him to decide, based on how he operates now and any plans for the future, potential resale value, or any other metric that may be relevant to him.

The 240 Vac emergency bilge pump will not be running off batteries and the whole concept of two independent power sources is to account for possible failure of the main genset.

Yes, of course. There's a centralised pump in the main mach'y space with rigid piping routed to each WT compartment led back to the pump through a valved manifold. If a raw water pickup is included and pump sized appropriately this can also be used for the fire main (Lazzara likely does not have this). Number of pumps and minimum flow rates are typically spec'd per size and category of vessel.

Submersible DC pumps are generally not considered part of this system by most regulatory bodies, although may be used for convenience nevertheless.

Yes he can, there are (2) DPDT switches with shore power and main genset inputs with loads split into groups A and B. These should be shown on sheets 3 and 4, respectively.

Sounds like a solid set up. My own yacht has a small belt-driven pump off the single engine in addition to the main electric-driven pump, probably routed a similar way. We don't have a fire pump though

When I looked into this, the easiest solution we found was running the generator output wiring all of the way up to the main panel, I think it was in the salon, and running it to where the main generator wiring was switched over from shore, and adding another breaker/slider and switching it there, that way you could run everything from the boat on it. I think the panel in the engine room where you switch over to the emergency gen now, is stuff you would always leave on anyways so didn't have to go to the engine room if you switched it up in the salon. You would have to shut some systems off to run it, but could get 50 amps out of the small generator or so.......the owner backed out of the purchase due to the excessive cavitation getting on plane and some other issues found on the survey so we never pursued it, and this is going back about 6 years now.

Trending to staying out of this discussion as to not enough information for a clear response, and now spooked by the concept that one might remove the safety slide.

But it would seem easy enough to simply run both legs of the service side of the supply switches to the same terminal, where they are protected from each other by the slide switch, and let both dual legs feed the main panel. Yes, you'd have to manage the loads via breakers, but at least you could power the devices that you must have up to the limits of the supply...

Mine is set up this way with multiple incoming shore and generators, all managed by slide safety switches, all feeding the same terminal bars. But the photo of the backside of the slide switch suggests to me that one incoming leg is not used to feed anything at this time? Are all items it powers presently single leg 120v? Is there power to the leg without a service line leg? Confused a bit...

Mine is complex at first glance. But then once you understand what you're looking at, it's pretty simple. Each incoming supply from shore or generator (2 each) pass through their own primary breaker, then at the panel they enter their own supply breaker amongst a slide switch and parallel to spread the load, not much unlike the single slide switch posted above. Mine has two slides, each with a shore and a generator breaker as well as a parallel breaker. You choose the incoming power you want on one slide, and then engage the parallel on the other slide to power both buses of the main panel. Again, complex perhaps at first glance, but then it's really straight forward and logical.

In theory one could run each bus off one generator by not using a parallel breaker. The theory works, but I haven't tested the circuits to rule out any AC contamination across the buses....scared to find out the bad outcome occurs...