We are dealing with requirements to get air into the engine room of my one- off custom 48' express tournament sportfishing boat. We've installed tow Yanmar 8y-STP 900 hp twin turbo "V" 8's and one Norpro 12.5Kgen set. Now I've seen the typical side louvers and the side panels that are used by Cabo on the 52 Express. I've also noticed boats that don’t' have any vents on the side that must be getting air into the engine room from vents under the gunnels or vents that lead into the cockpit via some other means. But what I'm looking for is experience and thoughts on engine room ventilation. The air box was built on the 2 sides of the engine room with the thought of cutting in and making louvers. I think it will take a lot of time to make these custom louvers contoured to the hull. I'd prefer to spend my money on something other than having the crew mold the hull and then painstakingly build the custom louver area. I told them I think the panel with the perimeter cut out would be fine if we rout in some recessed detail to it. It would certainly be easier to keep clean than louvers. I was told that it might not be able to be done as a result of the air flow requirements. But my answer to that is Cabo is doing it. I also like the clean look of no louver so that would mean concealing the air intakes in the cockpit and that could be done easy enough since we haven't started building the cabinets yet. I could mount them on the sides of the cabinets between the gunnels and the cabinet sides. And I have plenty of cabinet space back aft so I'm not concerned about that resulting in lost cabinet space. So my questions are. Are any of you running boats with concealed air vents? If so where are they ducting to? What’s the end result with regard to engine room noise being transmitted through the vents? To the builders: The boat is a plank on frame with 2 layers of bi-directional plywood on the outer skins. How many hours should it take to make louvers to fit the shape of the hull? Keep in mind that the air boxes are built on the interior. Are there standard components available to build these?