Propane powered bilge/trash pump - revisited

[Singularity]

In the process of converting my boat to 24v so of course all the pumps need to be swapped. In evaluating the emergency bilge pump situation I'm fundamentally unimpressed thinking through most scenarios with electric pumps, as are most I'm sure. So in addition to the electric low volume and high-volume bilge pumps (and manual) I'm thinking about a trash pump...

The topic of gasoline and maybe propane powered trash pumps has come up a few times, but I've not see someone having installed one. I'm looking at buying a $175 (on sale/communist member price) pump from Harbor freight and installing a $30 bi-fuel carb (with excellent reviews on Amazon and youtube) that would allow propane use. Add $50-75 for hoses and the total investment isn't far from the cost of a high-volume electric pump of questionable utility once the batteries are submerged (plus the trash pump might offer utility in firefighting, depending on where it's stored).

The main question is: has anyone installed or seen someone with one of these? Problems encountered or predicted? Thoughts?



The water movement with these things is impressive.
https://youtu.be/A0Gcwg7zasE
https://youtu.be/rk2QhBy6EXM

[Dockhead]

That sounds like a good plan to me.


I think your assessment is right -- standard bilge pumps, even large ones, will not do the job of dewatering the boat in a flooding emergency.


My solution is a very large trash pump with folding fire hose, which runs off 230v AC power. But I have a heavy duty generator above the water line to run it with. In the absence of that kind of power source, then I think propane is actually the best solution, because of the risk of carb gumming on a petrol one (plus difficulty of storing it), and because diesel ones are just too big.



I generally hate propane -- it's inherently dangerous on a boat -- but if you have it on board anyway, this is, in my opinion, a really appropriate use case for it.


Besides trash pump you should, of course, have maintenance pumps and volume pumps in each compartment, but I think you know that.



Don't forget a bilge alarm, without which pumps might prove useless (once the sole boards start to float, it may be too late).

[GordMay]

In an extreme crisis, I don’t think I’d like to rely on a pump from Harbour Freight. Firefighting, and sinkings are not the exigencies, wherein original capital cost should be your priority.

[Singularity]

To clarify my thinking...

I have plumbing in place for both a maintenance and an emergency electric pump. These will be utilized accordingly. If I want to add a second emergency pump...in addition buying another electric pump...I'll need to poke another hole in the hull (or experiment with manifolds, y-valves, etc). Then hope that my below the waterline batteries and genny can feed the electric pumps with significant water present for a good while...while also hoping that the electric pumps don't foul.

Thus in my circumstance an alternative to the second emergency electric pump is a propane powered pump that frankly costs less than the second emergency electric pump. I reckon, maybe wrongly, that ultimately a serviceable and routinely preventive maintained lowly harbor freight trash pump would offer superior utility in the life (and incidentally boat) saving department. Cash saved can go into another epirb or something.

FWIW I've ordered the carb, will pick up the pump this week...will report back if I survive the experiment.

--

As an inside joke to Gord...this is an example of synchronicity (when evaluating harbor freight products)...about 15 seconds into this clip from the comedy movie 1941:

https://youtu.be/RmLAA2r4DlA?t=57

[Scubaseas]

How are you going to handle the exhaust?



How much propane do you store? Propane consumption rates for converted petrol engines is surprisingly high. Be prepared to have lots of propane on board.

[AJ_n_Audrey]

I have a Honda WX10 trash pump for emergencies. I keep a can of unopened True-Fuel on board to use to start it - I have found that to be key to reliable starting. That said, I've never had it on board longer than a couple of months (my longest trip), so as for long term storage, I'm not sure how I would do that. I've thought about trying to find a super-large zip-lock bag or something, but so far have not done it.

[Russ]

Google
Fast Flow Emergency Bilge Pumps

Engine shaft direct drive ( no belts etc) and your diesel will run underwater till air flow submerged. It is an in place always ready pump. Time usually is of the essence when taking on water.
Mine cost $1,000 for my 42ft cutter.

[HopCar]

I like the idea of propane fuel for an emergency pump that will not be used often. I own propane Outboards and generators. They can sit for months and still start right up.

A dual fuel conversion is even better. Just don’t put gasoline in it except in an emergency.

From my Outboard experience I’ve learned that it takes about one pound of propane to produce 2-1/2 horsepower for one hour. The Outboards were designed to run on propane with a higher compression ratio. A converted gasoline engine might produce less horsepower per pound of propane.