2nd bilge pump

[BigTerp]

Going to get a 2nd bilge pump. Tore a hole in my hull last summer and the 750gph I currently have couldn't keep up. My current pump is 5200'd down to my hull in the starboard side of my bilge. I keep a 2 gallon spare gas can and my anchor on the port side of my bilge. Planning on installing the new one right beside my current one to keep wiring simple/easy (just tie it into my current pump wiring) and to keep the other side of by bilge free for storing my gas tank and anchor. Any issues anyone sees with this? Or should I have a pump on each side of my bilge?

 

[lugoismad]

Going to get a 2nd bilge pump. Tore a hole in my hull last summer and the 750gph I currently have couldn't keep up. My current pump is 5200'd down to my hull in the starboard side of my bilge. I keep a 2 gallon spare gas can and my anchor on the port side of my bilge. Planning on installing the new one right beside my current one to keep wiring simple/easy (just tie it into my current pump wiring) and to keep the other side of by bilge free for storing my gas tank and anchor. Any issues anyone sees with this? Or should I have a pump on each side of my bilge?

I'd go for a pump on each side.

Now you're scaring me. I only put in a 600gph.

 

[DaleH]

Definitely plumb the other pump's outlet out the other side! For if or WHEN the hull heels, you still have pumping capability.

 

[BigTerp]

Definitely plumb the other pump's outlet out the other side! For if or WHEN the hull heels, you still have pumping capability.

I would definitely have a separate outlet for each pump. But now that I'm thinking about it, having another pump wired to my trolling motor battery instead of my starting/accessory battery might be a better option. If ever I were to lose power, for whatever reason, I would have a back up pump on a back up power source. Just hate to loose that bilge space where I store my gas can and anchor.

 

[lckstckn2smknbrls]

Have one pump on a dash switch and one a float switch.

 

[BigTerp]

Now you're scaring me. I only put in a 600gph.

It's amazing how fast a boat can fill up with a 1" x 1/4" gash in the hull.

 

[DaleH]

Now you're scaring me. I only put in a 600gph.

It's amazing how fast a boat can fill up with a 1" x 1/4" gash in the hull.

My offshore 25' Parker (for sale BTW) has the capability to pull from 5 pumps totaling 5,000 GPH as my livewell pump is plumbed to a 'Y' valve so I can switch it from pumping from the seacock to pulling raw water up and out of the bilge (to the livewell hose that I'd direct overboard).

And do you know why? Here's a lesson my offshore days/experience taught me ...

A 2" hole only 1' below the waterline will let in ~78-gallons per minute. That is 4680 gallons per hour! Plus, at typical 8.5 pounds per gallon for saltwater, that is 663 POUNDS per MINUTE being added to the boat. Holy s#$t that's a ton of weight!

 

[slick]

I would set a spacer under the 2nd one (if it has a float switch). It takes less battery to run 1, but you will have the luxury of the 2nd pump in an emergency or if the first quits .

 

[BigTerp]

Thanks for all the suggestions.

Going to go ahead and install one separately on the port side of my bilge and wire it separately to my trolling motor battery. Just need to decide if I want another 750gph or an 1100gph.

 

[Johnny]

I agree with the two pumps idea: one on a manual switch, one on a float switch.
biggest-baddest-highest capacity you can find on the float switch with 1" outflow plumbing.

I just purchased a "ready to go" 1648 MV bass tournament boat a few months ago.
when inspecting the bilge pump, I saw it was way too small for my peace of mind.
Upon installing a new bigger pump, I saw the existing 3/4" outlet hose was cracked behind the wall of
the hull and when used, it would pump probably 50% back INTO the boat - very scarey thought.

So, make sure your pumps are free of debris and the impeller turns freely,
inspect the outlet hoses and fittings to ensure they aren't dry rotted or kinked and all works well.

If you are not sure of the pumping capacity of your pumps, put in the drain plug
and with a water hose, put about 4 inches of water into your boat...... then turn on your bilge pump
and you will be SHOCKED at how long it takes to pump out just 4" of water......








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[PSG-1]

I have 4 pumps aboard my jet boat. An 1100 GPH, an 800 GPH in the engine compartment. As well as a siphon-fed bilge that's hooked to the jet unit, guess-timated capacity is about 250 GPH.

Also, I have a 500 GPH automatic pump on the deck of the boat, since it is independently sealed from the engine compartment. Any water on deck, stays there, rather than going into the engine compartment. That was an improvement made to the boat when I upgraded to the 4 stroke, after the 2 stroke got destroyed from being swamped by a para-sailing boat.

So, with my 4 pumps, I can run about 2650 GPH out of my boat.

It might sound excessive, but trust me, when one of those para-sailing boats, or one of those 26 foot twin engine T-top booze cruising ocean cowboys rolls past at half throttle with his bow at about a 75 degree angle (I guess they run like that so they don't have to tip their beer back as far to swill it) and it throws about 2 or 3 waves over the bow and fills the boat knee-deep....you can't get the water pumped out fast enough.

 

[Snowshoe]

I wouldn't be storing a gas can in the bilge area.

 

[DaleH]

2 things ...

-All bilge pumps are rated at the outlet, so if you have poor wiring and a long hose run or high lift to get it outside the boat, that 750 pump might perform like a 300-400 GPH one.

-Use internally SMOOTH-bore tubing, as any spirals or corrugations like used on typical bilge hose ... robs you of an additional 10-20% efficiency due to losses for resistance and turbulence (Bernoulli's theory of hydronamics)

 

[BigTerp]

I wouldn't be storing a gas can in the bilge area.

Why not? It sits right next to my 6 gallon plastic gas tank.

 

[BigTerp]

2 things ...

-All bilge pumps are rated at the outlet, so if you have poor wiring and a long hose run or high lift to get it outside the boat, that 750 pump might perform like a 300-400 GPH one.

-Use internally SMOOTH-bore tubing, as any spirals or corrugations like used on typical bilge hose ... robs you of an additional 10-20% efficiency due to losses for resistance and turbulence (Bernoulli's theory of hydronamics)

Thanks. My run is pretty small, probably 2' worth of hose and a lift of about 1' or so.

What tubing would you recommend and where can I get it? I used a Shoreline Marine kit for my 750gph pump. It uses the corrugated/spiral hose you are referencing.

 

[Johnny]

any smooth bore plastic hose.
Personally, I had some 3/4" and 1" irrigation hose that worked great for my pumps.
I used 90 degree elbows instead of trying to get the hose around tight bends.
makes for a neater job also.

 

[slick]

You also lose pump capacity for every elbow or coupling installed. I have seen people use reducing coupling on the pump and larger pipe onward and outward. I wasn't sure how to word that. I typed the first thought that came to mind.

 

[DaleH]

In fluid dynamics, elbows or corners have more flow loss effect than transitions like couplings. What happens to water flowing through a pipe is the loss of intertia; the water is flowing until it hits the corner, loses the energy in motion it had built up and needs to rebuild it at that point forward.

There are many variables, but I know in pipes around 1-1/2", one 90-degree elbow is like putting that fluid through 7 more feet of tubing. Add any vertical lift into the equation (called 'head' in plumbing terms) and they'll be much more loss.

Smooth bends are preferred vs using elbows. However with that said on those pumps where one can use an over-size hose, that is one way around it to still maintain a minimum flow, at least when using elbows where needed.

 

[BigTerp]

Thanks again.

Going to go with an 1100gph installed on the other side of my bilge and instead of using the "standard" bilge hose will be picking up some Shields 148 series smooth bore VAC extra heavy duty hose. Going to get some 3/4" hose as well to replace the "standard" bilge hose on my other bilge pump. Should have done all of this last summer after punching a hole in my hull and realizing my 750gph pump wasn't quite enough. Better late then never I guess.