Using Your Engine as a Bilge Pump

[Bash]

I did a delivery on a 100' motor yacht that had such a setup. You could clear a foot of water out of the bilge in seconds.

[capn_billl]

A number of power boats have this setup, the theory being the engine will be the last thing to fail.

I like to have as many ways of getting water out of the boat as I can.


For the ultimate safety, (for starters eliminate as many as you can, ways water can get in to start with), then think about each potential failure you have left, how much water will come in? What sized pump do I need to keep up long enough for me to fix it?

[Pau Hana Daz]

We have this set up on Pau Hana as our 4th line of defense. (first is a Rule 3700 GPM electric with a float switch, 2nd is our diaphragm sump pump with float switch, 3rd is a manual Whale pump in the cockpit, 4th is the Yanmar with a 3-way valve)

What I did was install a bronze 3-way ball valve between the intake seacock and the main strainer. Normal operating position has seawater flowing from the seacock through the valve to the strainer and on to the engine. The 3rd leg of the 3-way valve has a length of hose attached to a bronze strum box in the bottom of the bilge. In an emergency, all you do is close the main intake seacock and turn the 3-way ball valve. Water from the bilge is strained at two points (the strum box and the main strainer) before reaching the engine. As mentioned previously, this set up also allows one to easily flush the system with fresh water (or antifreeze) from a bucket or hose. We keep a small cable tie on the valve handle so it is not accidentally opened (it's easy enough to break the cable tie when you want to open the valve).

We also have a 3rd float switch mounted above the pumps. This switch is wired to a marine horn in the cockpit. The theory is that is the electric pumps (or switches) fail and/or the pumps are overwhelmed (~10" of water), we'll get an auditory alarm letting us know about it before finding water in the salon/cabin as our bilge is several feet deep where the pump pick ups are located.

[Canibul]

Am I missing something? that valve looks tied OPEN,already.

[Cheechako]

It's been done many times, but lets face it... that's a real slow pump! Put your money in an extra pump...

[delmarrey]

Originally Posted by Cheechako

It's been done many times, but lets face it... that's a real slow pump! Put your money in an extra pump...

That would be my other reason for not using the motor pump, too slow. I'd have to be running the motor at full speed to get 8 -10 gpm.

[Pau Hana Daz]

Originally Posted by Canibul

Am I missing something? that valve looks tied OPEN,already.

It's tied OPEN between the seacock and the strainer and CLOSED between the strainer and strum box (notice the "flow" indication/label on the handle). Pulling the handle up routes water from the strum box to the strainer and engine.

[Celestialsailor]

Well...Like I said earlier, while testing my rebuild on the hard, I could empty a 5 gallon bucket in about 30 seconds at 2000 RPM. That's not too shabby. When Rule or Atwood measure their pumps it's with zero head pressure. Often times a bilge pump has to rise 10 ft. to get out of the boat. A Rule 2000 quickly becomes a 500 with that kind of lift. A cheap 3-way valve for the raw water intake is a good addition to your safety.

[HopCar]

DW, Does the hose with the blue stripe go to the strum box? Looks like you don't need to close the seacock to pump the bilge, just move the handle on the 3-way valve.
When water is coming in the boat you will want all the pumping capacity you can get. I bet DW doesn't have fifty bucks into his set up and he's added a 1" engine driven impeller pump to his pumping capacity. It can't hurt.

[Tellie]

I agree with Cheechako, invest your money in another pump.
I would never jury rig anything that might compromise my boats propulsion in an emergency. Raw water impeller pumps are famous for shredding if run dry for more than a few moments. If you are in an emergency situation where water is coming into the boat it's very probable the last thing you want is a diesel that has just overheated from a destroyed impeller that's sucking air as water sloshes back and forth in the bilge or more water is pumped out than ingresses. It's one of those things that look good on paper but not practical in reality and can increase the possible danger you're already in.

[sabray]

I have this set up on a cummins 4b3.3. Great for flushing and winterizing. Ill try to remember to get a picture. I used it once to get water out in a hurry. It worked a charm. Not sure how much water but enough so I didnt care I wanted it out fast. it was pretty quick and noticeably got the water out faster. Not a bad set up for a back up.

[Pau Hana Daz]

HopCar - Yes it does. You're correct, I really don't need to close the seacock to pump out the bilge, but it just seems like the right thing to do...

Tellie and Cheechaco - I kind of agree with you. I added the 3-way valve when I replaced the intake hoses and rebuilt the seacock and strainer. I wouldn't recommend it as a primary backup, nor would I plumb it in place of another pump. I did add it as a fourth pumping option (second non-electric). I figure that if there's a bunch of water coming in, I want to have as many options to pump it out as possible. YMMV

HopCar is correct in that adding the 3-way valve was inexpensive. Much cheaper in fact than adding another electric or manual pump.

[Bash]

Originally Posted by Tellie

I would never jury rig anything that might compromise my boats propulsion in an emergency.

When I've seen this done on yachts, it's in no way a jury rig. Nor is it done in place of back-up bilge pumps.

I want to do this on my boat, but it's still pretty far down on the wish list. If/when I finally get around to it, this will function as my fourth pump. If the other three couldn't keep up with a leak, I wouldn't hesitate to get an assist from the diesel exhaust system.

[cal40john]

Originally Posted by Celestialsailor

Well...Like I said earlier, while testing my rebuild on the hard, I could empty a 5 gallon bucket in about 30 seconds at 2000 RPM. That's not too shabby. When Rule or Atwood measure their pumps it's with zero head pressure. Often times a bilge pump has to rise 10 ft. to get out of the boat. A Rule 2000 quickly becomes a 500 with that kind of lift. A cheap 3-way valve for the raw water intake is a good addition to your safety.

I've seen engines that pump what looks to be a lot of water,others not so much. I hung a bucket under my exhaust of my 3GM30 and timed it. At idle 2 GPM. Assuming linear response, 9 GPM at max rpm. That's not worth it to me, I'll mount an impeller pump with a manual clutch for around 60 GPM instead.

I thought I was being conservative derating the Rule pumps by half. Rule's chart shows a 16 foot lift to derate to 1/4 the output. You said many installations have a 10 foot rise, if you have the output 2 feet above the waterline, that's an 8 foot deep keel you have your pump in. I sense exaggeration.

Besides the larger pumps don't need to be installed in the lowest place on the boat. My 3 GPM Par diaphragm pump goes to the bottom of my 5.5 foot deep keel, as do the 2 manual pumps. The Rule sits on the lead in the keel, maybe 2.5 feet below the waterline. Less height to lift,still lots of keel to fill with water before it gets up to where things are, and I have an alarm on it to let me know an unusual amount of water is in the boat.

John

[Sam Plan B]

I installed a bilge intake a couple of years ago. It's a simple thing to do. Cut the raw water hose (close the cock first) and intall a bronze T with nipples at each end. Add another length of hose from the T to the bilge. Put a bronze strum box on the end of the T hose. It is very useful when winterizing the engine. Just put the T hose in a 5 gallon bucket of anti freeze and run the engine. It will empty 5 gallons in about a minute and a half. Kill the engine before the bucket is dry.

As for using it for an emergency bilge pump, that's why in installded it. I read about it in a William McFee novel. They had those on steam ships.