I have a 230 so don't know exactly what the setup is on the 240s, but for me, in our 230, I keep all the interior plugs out. This was the 1st boat I had seen with so many interior plugs. I installed a backup bilge pump and if water finds its way into the boat, I want it to quickly find a way to the bilge to get pumped out. 2 of the plugs in the 230s do not even really make sense, the 2 at the bottom of the engine tray. The engine mount tray lip is so small, really, water is going to fill up and spill over anyways, so what's the point? But what does happen is it rains or people are wet, whatever, and in that small drop between the rear seats, water overflows into the engine compartment and I would sometimes find water (I have no engine leaks) under the engines and all the plug was doing was keeping it there now constantly splashing against the bottom of the engine.
When we bought our boat (used), it had literally just gone on the market, and from just a few days rain, even with the rear drain plug out, the floor locker and fuel tank area, etc were full of water and there was water under the engines, all most likely from rain and all because the interior plugs were in.
If something major happens, at least in a 230, IMO, all those plugs are not going to make a difference. People talk about blowing a plug and water quickly making it almost to the top of the engines, well, again on a 230, water would already be spilling into the fuel tank area via that huge notch on the port side for the fuel fill hose. Do the plugs have the potential to maybe slow things down? Sure, but IMO, barely. If water is coming in faster than it can get pumped out, it's going to happen. What would be nicer, if only it was easier to do, would be to change the fuel tank one to a scupper type. I wish there was a way to change the floor locker also to a scupper type.
Water routinely makes it into the boat, whether it's rough waves, or even rain. I want that water to get to the pumps to get removed. Last thing I want is a torrential down pour or a huge wave and my floor locker is full and water is in the fuel tank area and it's not getting pumped out.
If something serious does happen, I open my engine hatch to see a lot of water, then yeah, I will then put the fuel area and floor locker plugs in and then figure out what is going on, but at the same time, I wouldn't be expecting those plugs to save the day, just buy me time, be it minutes or seconds, not hours.
In normal every day operations, what are you more worried about? Sinking or making sure all the water that gets in your boat (from normal things like rain, waves, etc) gets out? There is enough flotation that the boats don't sink but even with all the plugs in, water will eventually fill all areas and the boats won't float enough to keep the engines 100% dry, so I don't bother with the interior plugs anymore and just let them sit out.
