have one but only because there was a hole I needed to fill. I had a gusher 30 and it worked fine for years but the seal seats went south so I replaced it with the gusher 10. I use it once in a while to make sure it's still working just because I won't allow anything on the boat not to work. Not because I think I'll ever need it. I used a manual pump once on a boat taking on water for an hour or so and what I have to tell you is that you won't be able to keep pumping in an emergency for very long. Put in a small manual pump for getting the bilge pumped after a rain storm but get yourself a high capacity electric pump for everything else. I always suggest that you also carry a Jesus Pump as well. For those of you who don't know what a Jesus pump is, it'd the pump that everyone rushed for when someone yells "Jesus! Get the pump". It's just a really, really big pump... Mine is an AC powered 3500 gallon an hour bronze trash/sump pump with collapsible hose. Let's take inventory. I have the wash-down pump which can be valved to be a bilge pump, I have two 500 gallon per hour bilge pumps and a 1000 gallon per hour pump that are permanently installed. Then I have the 3500 gallon trash pump and and an additional 12V 1500 gallon pump with a cigarette lighter plug and collapsible hose and the Gusher 10 manual. Then, if the water gets high enough I can turn on the shower sump which is another 500 gallons per hour. Over kill? Maybe but then I hope I never have to find out. Hey, what can I say, I also carry 4 big anchors.