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
Yeah I’ve had many problems with them too, I didn’t realize there was an alternative. I’ll check out the ultras thanks.
I'm not sure how the 42' is set up but on my 50', the two plugged drains only go to each self-contained fuel tank compartment. There is a main channel that runs fore and aft with limber holes in the stringers all throughout.
While you're at it, remember that most Posts' lean bow down at rest. This means that any water intrusion or spills from the engine room, (pits don't drain) sinks,water heaters DC or ac fresh water pumps and raw water pumps, all flow to the bow. That's a good place to have at least two serious pumps. One a few inches higher than the other. When underway be sure your high water alarm is working. I would like to have a louder horn but in a rough sea my float switch can fly open and give me a short ring with no water.
My fuel tank is in the center of the cockpit bilge, between the two deck boxes. So no separate fuel tank compartments - just 3 bilge compartments: forward, engine room, and aft
I'm intending to replace our several Rule swing-arm float switches -- as they age and fail -- with Ultras, as we did on the previous boat. The other day I noticed the Rule-Mate pumps, which have some kind of built-in switch... so I asked... and Xylem answered that they use a "field effect sensor to activate the motor." Don't know what that is... but in our situation, pumps with built-in switches could clear a bit of clutter. More expensive, though. Also, their largest Rule-Mate is only 2K, so probably not appropriate for a high-water pump. Also, the Rule-Mate installation diagram says to NOT use a check valve on the outflow hose; dunno what that would be. -Chris
Not sure exactly what you are pulling on with the last question but generally a check valve keeps a fluid from flowing “backwards” in a system. I don’t know why anyone would put a check valve on a bilge pump outlet though. Maybe if they were worried about the overboard discharge being submerged?
if the bilge is too small and the hose run too long, the amount of water flowing back into the bilge can cause the pump to cycle on and off constantly. I don’t like check valves on bilge pump discharges but sometimes it s the only way. I hate rule Mate pumps. I be had a couple in tenders and it’s only a matter of time till they fail. Nothing beats a standard pump and ultra switch
Another vote for Ultra Switches. Trip from NJ to Fl in previous boat found the lazarette completely full of sea water after the gen failed but it never entered the ER. Bertram had some type of step up thing in the keel area. H/W rule alarm switch was bad as well as the same type on the aft pump. Switched to manual and after an hour pumped dry. Strange thing was never found the source and over the next 20 or so years never leaked again. Trashed all the Rule switches and replaced with Ultra. Had a wiring issue with one of them so called the company in S. Fl. Owner answered and was extremely knowledgeable with Bertram's wire colors that differed from the diagram that came with the switches. New to me Bert already has all Ultra Switches. Not cheap but IMO worth the $$. O and make sure of voltage first, as they come in 12 and 24.
Meant to have typed "dunno why that would be." But mostly I was thinking about potential backflow, as Pascal mentions. Can't say as I've ever seen a check valves after a bilge pump, but then I also haven't closely inspected that on every boat I've ever been close to... You've tried the Rule-Mate pumps? What usually fails, the pump, the sensor, or the switch? -Chris
