I have a 31CB, but perhaps it’s similar. There is is no external intake. There are gaps inside the boat between the engine compartment and the storage lazarette underneath the cabin floor and near the aft bunk. Those gaps cause the cabin to heat up and engine odors enter the cabin as well. Interestingly enough, during a coast guard stop last season on the ICW is SE FL, I was told that I needed an engine blower even though I have a diesel. I told the officer that it was my understanding that one is not required for a diesel engine and he was adamant that it was required though I didn’t get cited. Further investigation clarified that I was indeed correct that a blower was not required but recommended. I intend to install a blower at some point that draws air in through one of the ports already in the cockpit floor and out the other one, and install a cowel on each that won’t allow water to intrude, and remove them when we’re not operating the boat. Then I can block all of the entry from the engine compartment to the boat living and storage spaces in order to prevent engine heat and odors from getting in. The Volvo Penta D4 320 requires fresh air so a blower would be a great addition. All of my other boats in the past had blowers, gas or diesel, so I was surprised that there is not a provision for one on my 31CB.
