I didn't give details because as I mentioned above, many people want to give their interpretations of the rules instead of hearing from an actual surveyor.
1992 Mac26s (25'10") with a permanent 12 gal "plastic" type tank installed in the lazarett. It has a remote fill (non metallic) and it is vented outside the lazarett into the outboard motor well. It also has a 3" exhaust vent with a duct running down into the bottom 1/3rd of the lazarett also venting into the outboard well. There are electrical components and wiring in the lazarett. There is no weatherstripping on the lazarett lid. There is one hawsepipe on the port side of the motor well.
I have no actual intake vent yet. (other than the two mentioned openings explained below) I'm not excited about putting a vent in a location that water could enter easily. I was wondering if another vent in the outboard well be ok? Another location might be in the cockpit facing forward.
Also, on the Mac26s there are two openings into the lazarett from the main cabin. They are located at the top of the lazarett and located on each side. They are large enough to stick your hand through. There are several wires / cables going through each openings. (Neither opening is visible from outside of the lazarett.) Are these openings required to be sealed? What methods of sealing would be permitted?
"188.8.131.52 Openings such as crevices, holes, joints, and penetrations for wiring, cable, and hose, etc., in bulkheads or decks between accommodation compartment(s) that are adjacent to, or above a compartment(s) that contains a gasoline engine shall be constructed to minimize the flow of gas or vapors from the machinery space by means such as, but not limited to, flexible compounds." This item refers to a gasoline engine not a fuel tank compartment. Would it be the same?
I understand ABYC is a business and they own the copyrights to the information they publish. Also surveyors should be compensated for their time but since the USCG doesn't publish actual standards, how would any individual be expected to do modifications properly? Would the ABYC "compliance guidlines" (comp005) ventilation, have the proper information?
There are a number of standards that could come into play but you did not ask any specific questions or tell us what you have diesel or gas..
H-2 Ventilation of Boats Using Gasoline
H-24 Gasoline Fuel Systems
H-25 Portable Gasoline Fuel Systems
H-32 Ventilation of Boats Using Diesel Fuel
H-33 Diesel Fuel Systems