Re: Propane leak into the bilge. What to do?
I served on submarines where evacuating toxic/explosive gases and replacing them with clean air is a daily part of life. There is a factor called the "half-life". The half-life is the time that it takes to replace HALF of the atmosphere on the entire vessel.
A recreational sailboat (even a serious cruiser) is much smaller than a submarine, so the half-life is considerably shorter.
In your scenario of a catastrophic hose or seal failure, yes, an ignition proof blower like the one for gasoline marine engines is a good idea. Obviously, open all hatches and ports if weather conditions are calm enough. The diaphram bilge pump will not move a significant amount of gas.
If you disperse CO2 into the bilge, you could displace the propane from the bilge, into the main cabin.
To calculate your half-life, estimate the volume of your cabin (or bilge if you prefer), and the CFM rating of your ignition-proof blower, then calculate how long it will take the blower to move HALF of the volume of the bilge.
This will help you determine how long you need to run the blower, in order to clear the bilge of propane.
Hope this helps.
S/V Old Shoes
1973 Pearson 30 #255