I have to run beilge blower for two fricken hours to keep smell from entering cabin, My A/C must suck from every nook and crany in my boat to create this reak!. Last night I came back from a good day of running to gag all night with the sent of gas/engines. What can I do to keep this smell out of cabin.
Today I have doors open with A/C on to eliminate the reak. Your thoughts are welcome.
Mr. Bravo III

Gasoline vapors are much heavier than air. They flow to the lowest spot on your boat. Check every possible line for a potential leak. The carbs may be part of the problem or the fuel tank fuel vent system. Maybe a small tank leak even. This is not just a nuisance but an invitation for disaster. If you can't fine the source have a mechanic check it out. Be safe.

Hydrocruiser, it s not gas smell, you know, like a engine room in a ship freaking oil smell, I have a 390 express with a DRY beilge, no water/gas/oil.
just the stink of the engines till they cool down. Yeah my carbs do reak for a tad, I am just picky on interior scents. If I go down into my engine room I smell Big Blocks sleeping. Wow, I just realize my new smell, I changed the dang oil two weeks ago with castrol 20/50. that is my new smell, last oil change was Mobil 1. Its the stinky petrolium smell that bugs me.
My A/C sucks my cabin into a negative tip, thus sucking from all cracks.
B3

Actually a/c would pressurize your cabin, blowing air out cracks and gaps to your bilge area, maybe your bilge compartment does'nt have enough ventilation? or the vents maybe full of spiders or hornet nests?

Conventional oils are more volatile under heat as they can begin boiling off at 200 degrees c whereas synthetics are well into the 400 degrees c range before that begins and as the VI index shows you do get a lot more petroleam distillates boiling off from conventional oils. Synthetics have higher VI's and are much less volatile and resistant to breakdown. Conventionals can give off a "kerosene like smell" after a good run. That probably is it! Go back to Mobil-1.

AC neither pressurizes nor creates vacuum in cabin. They are typically mounted under vee berths and couches and pull in air from the cabin and blow it back out into the cabin.

If the rear unit is not properly sealed from the engine room area, then you can get bilge fumes pulled into it.

I'd say there is a definite air leak to the engine room and you need to try your best to find it.

HOW? good question...
If a can of refrigerant accidentally got a pinhole leak and was placed into your engine compartment where it accidentally leaked out its entire contents, a handheld refrigerant sniffer used in the cabin would probably find the point of entry pretty quickly...

Mcollinstn, thanks for the Idea. I will look into that sniffer Idea, since I am HVAC certified. No problem. I just got back from a hard cruise and this time no A/C on do to weather is cold again and rainy. No stink. its only when my A/c is on where I get the reak. I will snoop for holes to plug on bulkhead to engine room. Thanks B3

Check your pcv system. Blowby that's not sucked back in the engine and burned off will REALLY cause a cruisers engine compartment to stink. And it's almost impossible to seal the engine compartment from the rest of the boat so I doubt that's your problem.
Gary