Using Your Engine as a Bilge Pump

[Astrid]

I think one would really be better off with a dedicated high volume bilge pump clutched to the engine or one of the fast flow prop shaft types in addition to your regular electric bilge pump or pumps. If you have been damaged and are taking on water, you will quickly run down your batteries running the usual bilge pumps and since you will probably want the engine on anyway to keep charging the batteries, an engine driven pump of some sort would be good insurance.

[atoll]

it is pretty standard practise on fishing boats,that run 2 impellor pumps,so either can be redundant,or pump bilges or deckwash or engine cool

[Celestialsailor]

Originally Posted by cal40john

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.
John

Thanks for the shot. So here we go...pay attention...If draft is 6 ft. (which is aveage) and freeboard is 4 ft. (which is average) and the hose loops up under the coaming (as most do) then it's 10 ft. Why do we always have to shave freckles off an ants butt here. If your Yanny sucks 2 gl. a minute maybe it's pump is small...Heck I don't know or care. I empty a 5 gallon bucket in 30 seconds...ok?

[Brazil]

Originally Posted by Celestialsailor

Thanks for the shot. So here we go...pay attention...If draft is 6 ft. (which is aveage) and freeboard is 4 ft. (which is average) and the hose loops up under the coaming (as most do) then it's 10 ft. Why do we always have to shave freckles off an ants butt here. If your Yanny sucks 2 gl. a minute maybe it's pump is small...Heck I don't know or care. I empty a 5 gallon bucket in 30 seconds...ok?

Yes my boat has 10 ft lift and corrugated hoses that slows the pumps even further. I like the idea of a engine as a bilge pump.

[Brazil]

Originally Posted by Astrid

I think one would really be better off with a dedicated high volume bilge pump clutched to the engine or one of the fast flow prop shaft types in addition to your regular electric bilge pump or pumps. If you have been damaged and are taking on water, you will quickly run down your batteries running the usual bilge pumps and since you will probably want the engine on anyway to keep charging the batteries, an engine driven pump of some sort would be good insurance.

Yes a clutched pump connected to the engine is probably much better, but you can't compare it in cost, time and skills to install it with a T in the engine raw water intake. you are comparing apple to oranges here

[Brazil]

Originally Posted by 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.

Don't forget most people only would use it in the worst possible case , when the water Is much higher then sloshing in the bottom of the bilge and the risk to overheat the engine may very well be worthwhile

[HopCar]

Adding another engine driven pump would be better, especially if your engine cooling pump is small, but it's expensive and complicated. You've already got the engine cooling pump, why not use it?
I really like the idea of those prop shaft driven pumps. They can really move a lot of water. Unfortunately the engine has to be in gear for them to work. You may not want the boat to be moving while you try to stop the water from coming in. Figure out a way to belt drive one of those suckers and you've really got something. DW's installation is not a "jury rig" by any means. It's well thought out and properly installed. If my bilge gets so dry that the impeller burns up, the emergency is over and I've got time to change the impeller.

[cal40john]

Originally Posted by Celestialsailor

Thanks for the shot. So here we go...pay attention...If draft is 6 ft. (which is aveage) and freeboard is 4 ft. (which is average) and the hose loops up under the coaming (as most do) then it's 10 ft. Why do we always have to shave freckles off an ants butt here. If your Yanny sucks 2 gl. a minute maybe it's pump is small...Heck I don't know or care. I empty a 5 gallon bucket in 30 seconds...ok?

I didn't comment on your engine's output. I said some engines put out alot and some don't. My engine, for example, doesn't put out a lot of water so it wasn't worth it to me to use it as a bilge pump.

I was taking issue with your claim that the Rule pumps only 1/4 of their rated output. The height is determined at the outlet height, not the highest point that the loop attains. Your example of 10 feet would have to have the outlet at the top of the coaming. At 10' the pump is derated about half, you derated to 1/4, I don't consider that shaving freckles. Having the outlet 2 or 3 feet lower adds maybe another 10-15% to the performance. You could be correct for the 1/4 output though. Put the pump at the lowest point in the bilge, have the outlet at the highest point, use corrogated hose with tight bends, and use undersized wire, but do you complain about the pump or the installation then?

John

[Celestialsailor]

Originally Posted by cal40john

I was taking issue with your claim that the Rule pumps only 1/4 of their rated output. The height is determined at the outlet height, not the highest point that the loop attains.
John

Bull...The height IS determined by the highest point. It has to pump that high does it not? As for Rules chart. On their site is a pfd download manual. There is a chart a few pages down For a good example, the Rule 1500 pumps at a claimed 1500 at 0 ft. If look over at 10 ft., it is approximately 300 gal/hr. So, you're right. It's not 1/4...I apologize...IT'S 1/5! Also, I'm sure their tests are done without a check valve which they recommend you add. I'm sure that would hinder it more.

[cal40john]

Originally Posted by Celestialsailor

Bull...The height IS determined by the highest point. It has to pump that high does it not? As for Rules chart. On their site is a pfd download manual. There is a chart a few pages down For a good example, the Rule 1500 pumps at a claimed 1500 at 0 ft. If look over at 10 ft., it is approximately 300 gal/hr. So, you're right. It's not 1/4...I apologize...IT'S 1/5! Also, I'm sure their tests are done without a check valve which they recommend you add. I'm sure that would hinder it more.

You are right, my mistake to not be more careful. I went to the graph for the pump I have, the Rule 2000. All the pumps in the large pump section do 1/2 or better at 10 feet of head. The 1500 is in the small pump graph. If I knew that I had a 10 foot head to deal with I don't think I would select a pump from the group that has a discharge head (max height) of 12 feet. Once again a question of appropriate installation. Also we were talking about using the engine to help empty the boat, which to me means some kind of emergency and so I thinking big pumps. I should have been more specific.

Rule pump graphs: page 11
Rule manual stating no check valves: page 16
At:
http://lib.store.yahoo.net/lib/kingp...ump-Manual.pdf


The discharge head of the pump has to be higher than the highest point in the outlet hose. Once the hose fills siphon action applies. Static head is height difference between pump and outlet.

Pump system curve


Figure 11:zero static head
Figure 13a: discharge head
At:
HOW TO design a pump system


Video showing pressure in pipe going negative above pipe outlet:

IV. Pressure variation in the discharge line of a pump - YouTube

John

[Tellie]

Originally Posted by HopCar

Adding another engine driven pump would be better, especially if your engine cooling pump is small, but it's expensive and complicated. You've already got the engine cooling pump, why not use it?
I really like the idea of those prop shaft driven pumps. They can really move a lot of water. Unfortunately the engine has to be in gear for them to work. You may not want the boat to be moving while you try to stop the water from coming in. Figure out a way to belt drive one of those suckers and you've really got something. DW's installation is not a "jury rig" by any means. It's well thought out and properly installed. If my bilge gets so dry that the impeller burns up, the emergency is over and I've got time to change the impeller.

Let's eliminate whales, containers, logs and flying saucers. What's the most likely reasons and conditions that a boat at sea would be taking on water, and would you want to be engineless in those situations? People can do what they want on their boats. Just because they use quality parts for a design not intended doesn't mean it's not thought out to the best of their abilities and experiance. But then it doesn't mean it's not jury rigged either. There are people here, well intended, that think lawn sprinkler system parts will work fine below the waterline. Do they work? Sure they do. So will knob and tube on a boat. My grandpaps always said "The only thing a man needs is a roll of Duct tape and some bailin wire to fix anything. I'm not saying in a last ditch effort I wouldn't look to the engines raw water pump for help either. What's the saying about a scared sailor and a five gallon bucket? But then I wouldn't design a bailing system around a five gallon bucket before I left the dock either. I make my living working on boats and I see so many things that owners do that just plain scare me. Sailors are the worst offenders in finding the cheapest way to do things to subsitute for a proper system in the first place. Tell them they have to spend a few hundred bucks for a proper pumping system and a quality bilge alarm and they turn into MacGyver like Ol grandpaps.

[Celestialsailor]

Originally Posted by cal40john

You are right, my mistake to not be more careful. I went to the graph for the pump I have, the Rule 2000. All the pumps in the large pump section do 1/2 or better at 10 feet of head. The 1500 is in the small pump graph. If I knew that I had a 10 foot head to deal with I don't think I would select a pump from the group that has a discharge head (max height) of 12 feet. Once again a question of appropriate installation.

Actually the bigger the better I see with that graph. Knowing you have a Cal 40, your bilge which is just under the floorboards which affords you the luxury of a short rise. I always wonder how necessary these deep bilges are. Seems to me a moderate, say 2 cu. ft. hollow in the keel area would be perfect. Not these huge sink holes like I have.

[HopCar]

Tellie, I agree with most of what you said, I disagree that you are likely to damage your engine when using the cooling pump as an emergency bilge pump. You seem to be concerned that debris from the bilge will damage the impeller. The water is passing through two strainers before it gets to the pump, just like when it's being drawn from overboard. It's pretty unlikely that anything big enough to cause a sudden failure of the impeller would get through. If you're worried about sucking air and burning the impeller, you don't have enough of a problem to need to use the bypass.
If the cooling intake bypass is installed you have the choice to use it or not. If it is not installed, you don't have the choice.
DW used quality marine parts doing just what they were designed to do, direct the flow of water. I saw no sprinkler system parts. You are correct that boaters sometimes use the wrong hardware through ignorance and cheapness and sailors are the cheapest of all boaters. The wind is free and everything else should be. (Just kidding!) Don Gross, the owner of Groco, is an intelligent and experienced marine engineer. Don designed his Safety Seacock to allow you to do just what we're talking about. He seems to think it's a good idea and so do I.

Tellie, If you are ever in Miami at lunch time, drop by my store and we can continue this discussion over lunch. I'll buy.

[cal40john]

Originally Posted by Celestialsailor

Actually the bigger the better I see with that graph. Knowing you have a Cal 40, your bilge which is just under the floorboards which affords you the luxury of a short rise. I always wonder how necessary these deep bilges are. Seems to me a moderate, say 2 cu. ft. hollow in the keel area would be perfect. Not these huge sink holes like I have.

I draw 5' 7" and my bilge goes all the way to the bottom of the keel in the back, the lead is in the front of the keel. The top of the lead is somewhere around 2.5 feet above the bottom of the keel.

Cal 40 drawing:
Cal 40 documentation

Like I said in my first post I didn't put the big pump at the bottom of the keel. I already have 3 pumps that go down there, one of them a diaphragm pump with a relatively small pickup hose so it can get the bilge pretty dry. The big centrifugal pump with 1.25" diameter hose and 10 feet of rise would backflow almost a gallon of water when it turns off, so not a good choice for getting as much water as possible out in the end. I put the big pump on top of the lead because it was convenient, but I was looking for an easily accessible for maintenance spot and a high point. So it has around 2.5 feet less head to pump against. The big pump never sees water unless there is something wrong. There is an audible alarm to let me know when it comes on. And the pump is still low enough in the keel that I should be able to check throughhulls, close seacocks, and look for the leaks before the water completely fills the keel and starts flooding areas in the rest of the boat, except for those probably going to abandon ship style leaks. I've come across more than one website recommending mounting bigger pumps higher than the small ones.

John

[Astrid]

If you are talking about bilge pumps running off the batteries, the logic of having the bigger one higher up than the smaller ones makes some sense. The bigger pumps draw more electricity than the smaller ones, and you don't want to run down your batteries if dealing with something the small guys could handle ok, so you put them below the big boy which will then only kick in if the inflow of water is more than the the small ones can handle.