Recently I installed a manual Whale diaphram bilge pump and a Whale pump strainer in my TI. The project was just completed and today I conducted a sea trial of the finished project. I am very happy with the result and am checking this project off my to-do list. I am sharing this info in case it is of interest to any of you.
I set up the boat as usual, minus a few typically stowed items and then added 50 gallons of sea water (approx. 428 pounds). At this point, with me in the aft cockpit, the stern of the boat was awash. Then I pumped out the water at a comfortable pace. It took 7 minutes to get the water out of the boat. That's a rate of approximately 7 gallons per minute. When the pump was pushing more air than water I measured the remaining water. Less than a gallon remained behind. This test was done during calm conditions, a slightly different outcome could result during rough conditions.
The pros of this installation are:
Reliability is high as the pump is simple to operate, requires little maintenance, does not need electricity, electrical connections or switches (and the weight or space related to a battery) and the pump can be used without opening hatches and while still sailing. Additionally, both the pump and the strainer include one-way valves so back siphoning should never be an issue. The pump is installed below deck so it cannot be left behind nor clutter up the area above deck. I also feel manual plunger type pumps are not as reliable as the pump I chose to install. This type of pump is also more forgiving when confronted with bits of trash or sand than other types.
The negatives related to the installation are:
I have given up routine use of the twist & stow hatch in the aft cockpit. While I can still use it for items that fit in a small and narrow dry bag, the gear bucket I previously used no longer fits. If the bilge pump is needed during a calm it is difficult to pump the bilge and use the mirage drives simultaneously (but alternately pumping and pedaling works fine).
Following are a few pics: