| Bushwacker |
02-14-2013 10:47 PM |
There is much more to the issue of bilge vents than just preventing mold and mildew, although I have seen the mold/mildew issue discussed here on boats where the vents had been closed up.
SeaCraft was always one of the rare builders, at least in the Moesly/Potter era, that did NOT foam in their fuel tanks, for good reason, AND they installed hatches over the tanks so you could remove and inspect them for leaks without cutting up the deck! If you read some of the brochures from the early 70's, Potter bragged about that, saying it was NOT a good idea to foam in fuel tanks because of the corrosion it caused, but said it cost them more because "THEN THEY HAD TO VENTILATE THE BILGE"! That sounds like this is a USCG requirement; does anyone know for sure? The Moesly boats all predated the USCG flotation requirements, so none of them was filled with foam to my knowledge, and they all had clam shell type vents on the gunnels and/or engine boxes, whether I/O or O/B versions.
The rationale for no vents on some boats MAY be that IF there is no empty space for fuel vapor to collect, (i.e., the entire bilge is full of foam) then there is minimal risk of an explosion, since there isn't any way for air to mix with the fuel vapor. It's the vapor that's explosive, and even then, there is a relatively narrow range of "fuel/air ratio" in which it will ignite. (We all know an old carb'd engine won't start if it's flooded by a choke that sticks closed, nor will it start when cold if the choke sticks open!) If the foam is saturated with liquid fuel, it could certainly burn if exposed to air, but I'm not sure there is enough air in a foam filled bilge to create an explosion hazard. Maybe some fire-fighter members of the forum who are more knowledgeable than I can provide more enlightenment on this subject and/or correct me if I'm wrong about this theory!
Now I'm not familiar with the 1980's and later SeaCrafts, and maybe they're full of foam, so that might explain why they don't have vents. But the bottom line is that I believe the Potter-era boats with open spaces around the fuel tank were intended to have ventilated bilges to eliminate any explosive mixtures, so I would not eliminate the vents on one of them, or ANY IB or I/O model with the open space around the engine for that matter. Granted, there are fewer ignition sources with an outboard, but what about bilge pumps and solenoids for power trim and trim tabs, etc.? Seems like anything we can do to reduce the risk of an explosion from even a small leak (I think the fumes from a cupfull of gas = 1 stick of dynamite!) is well worth doing, even if the probability of ignition is small. And if you have a large enough fuel leak, I suppose one could argue that ventilating the bilge might make it worse by just providing enough air to create an explosive mixture that would otherwise be too rich to ignite! However the human nose can supposedly smell an explosive mixture, so I would think anything too rich to ignite would be real obvious. I had a very small amount of seepage around the sending unit gasket one time, but the gas smell in the cabin of my Seafari was overpowering and I've been a fanatic about sealing that gasket ever since! For that reason, I guess any boat with an enclosed cabin like a Sceptre/Tsunami or Seafari should have hull vents, even if the bilge is full of foam. The Seafaris were only built by Moesly and Potter, but I think SeaCraft Industries built some Sceptre's in the 80's; don't know if they had vents or not, but I think they should have even if they're outboards! Denny
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