Been scratching my head for a while about this and wanted to get the thoughts of the brain trust here. My Post 42 has 2 bilge pumps - one in the aft, between the rudders, and one in the forward/middle of the boat, between the head and bunk room. There is no pump in the engine room. The bilge areas are connected by a transfer tube and there are drain plugs installed to keep water from moving between sections. This means the pumps are not redundant to each other without manual intervention (pulling the plugs), and there is no way to pump water out of the engine room bilge without also pulling the plugs. There are “crash pumps” where the engines can suck water out of the bilge, but these seem wildly impractical as they’d need to be manned constantly to switch between the thru hull intakes and the engine room intakes as the water level comes down so that the engine doesn’t overheat/impeller doesn’t melt, also the intakes are so high the water would be up to the battery tray by the time the intakes are submersed. What was the design intent here? What is the safest way to run the boat? Should I pull all of the plugs so water can move freely between the compartments, or leave the plugs in so that a leak in one compartment can’t flood the whole bilge? If it’s the latter, I assume I should prioritize getting a pump added to the engine room ASAP, correct? Why would post have skimped on something like that?
Our 43 has an aft pump and a bow pump (under forward stateroom floor). They are defenatly connected, water flows to the aft pump running and to the forward pump (lowest point) static. The engine compartment drains also go into the "tubes" running between the forrward and aft pumps underneat the fuel tanks. The one visible engine room inlet is under the generator at the forward end of the engine room. Our crash pump valve opens to a large PVC line running back from the stbd raw water pickup, under the cockpit floor, to just ahead of and above the aft bilge pump. I agree it would be challanging to use as need to close the hard to reach raw water shutoff just enough to maintain enough flow from the crash pump pickup to keep the engine cool. Boatyard discovered one year at launch that if the crash pump valve is left open it will slowly flow into the aft pump area. It now has a bright red "normally closed" tag on it (as does the forward end of the fuel transfer line, it will siphon from the taller aft tank to the forward tank if left open).
I would install a standard service size electric pump in the ER and a larger electric emergency pump in the ER placed higher than the service pump. I had those crash pump style 3-way valves on my engine intakes too and I removed them. I feel they create a bigger chance of creating a problem vs. solving one.
Only two bilge pumps on a 42? That’s insane. it is better to keep the compartments isolated if for no other reason than preventing ER water to migrate to the clean forward bilge. Also makes it easier to search for a leak. what size at the two pumps ? i would add two pumps in the ER, a 2000 gph down low to handle routine de watering and a 3700 8 to 12 inches higher to handle an emergency. ideally the aft bilge should have a back up pump as well in case of an exhaust leak or a rudder failure. fwiw, I have five 3700 on my 53 Hatteras which originally had four 2000s. I sleep much better at night.
Ok thanks folks. It sounds like my intuition is correct - I should unplug the tubes to allow water to flow freely between the compartments for now, but as soon as practical I should install at least one pump in the engine room, if not 2, and should also consider a redundant aft pump. These things are cheap in the grand scheme of things. I prefer to sleep well at night, and the exhaust leak scenario is a scary one too.
And while you at it, don’t use Rule float switches… they re junk nowadays. Use Ultra Switches. More expensive but well worth it. That’s all I use now. i ve burned up 2 pumps because of the POS rule switches
