check the hose internal diameter...1 inch is a 400, 1.25 is a 450 and 1.5 is a 500. I haven't rebuild one, but have rebuilt a double diaphragm pump for pumping chemicals. You just need to remove a bunch of screws, change out the diaphragm and the the two flappers and you are good. Be advised that a manual pump isn't much use. You need to put an automatic pump on board, or preferably two...one small down low and the biggest you can afford above it. The small one (ala Don Casey) will be the working pump. It will live wet in the bilge and die about every five years. It will pump out your ice box melt water...shower water...etc...which end up in the bilge by design. The big expensive one will live the life of Riley above the fray, but it will live hopefully forever...waiting for a serious emergency...but you won't have to replace a $200 pump every five years.
As usual...I have purchased all the stuff to make this change to my boat...which currently has a 2000gph pump down low...but haven't gotten around to it. When picking out the big pump...keep in mind that they rate them with no head height and their actual ability to pump water up four or five feet significantly cuts their output. That's why I have a 2000....although it is almost certainly too small. The fact is that, for the most part an automatic bilge pump will save your boat from the type of small leak which might occur from poor maintenance...a leaky shaft log...a burst engine coolant hose...but is unlikely to save your boat from serious damage. It won't keep up to a hull puncture unless you can stick a cushion in it or somehow stop the leak. And the battery will drain to nothing in short order if the engine isn't running.
However, I encourage you to install a proper automatic bilge pump first, ignoring the even more useless manual pump. Most people use them to pump the small amount of extra water their automatic pump leaves in the bilge. Other then that you are far better served by a bucket than a 20gph manual pump. Think of how fast you would tire. Also, the shop vac concept has to go. An automatic bilge pump is not an option, but a requirement. It is your watchman to safeguard your boat when you are away. Get in the habit of manually cycling it every time you are aboard to verify operation and listen for the amount of water discharging out of the boat (you can hear it splashing). Most switches are three way (off, on, auto) switches for just such a reason. If you have one of the automatic pumps that tests for water by spinning/resistance, you can also train yourself to pay attention when it does so, to listen for the water. They are preferable in some ways because the number one thing to foul up otherwise is a float switch. They just mechanically fail or get something stuck in them...you get my drift. On the other hand, there will be a small battery drain from the resistance type. If your boat has the ability to charge the battery or if you install a small solar panel it will easily keep up with the drain as long as your boat isn't leaking!
I bought (but of course haven't installed) a switch that can sense the water level without moving parts. I still have a float switch now...which has been replaced once since I bought the boat along with the original pump. Both were dead soon after I got Triple Play and it was just expedient to do a like for like replacement...which I planned to change later (hence all the new, but dusty hardware sitting in my boat...I wonder how many other sailors ballast their boats with substantial quantities of yet to be installed hardware LOL).
http://www.westmarine.com/webapp/wc...toreId=11151&catalogId=10001&page=Bilge-Pumps
