Bilge pump installation: question regarding outflow

[axeslinger1957]

First off, I apologize if I posted in the wrong place. I'll try to come right to the point. My boat had nothing electrical when I got it last year. I am in the process of restoring functionality to it step by step. Concerned by things I've read here and not wanting to put family or friends in possible jeopardy, I've decided that one of my first spring projects should probably be the installation of a bilge pump -- especially since I'm reconfiguring that area anyway.

Most of the stuff involved I think I can either do myself or get some help. What scares the bejabbers out of me is drilling a hole in my fiberglass-covered transom. Here's my question: Forward of the transom, there is at least one hole drilled over the battery / fuel tank / bilge area. I don't know what you call this -- is it the bilge? For the purposes of what I need to know, that's what I'm going to call it. If I get something like an 1100-gallon per hour pump and then I were to run its outflow hose up through a hole forward of and above the transom, which would then dump over the transom, is there any reason to not do it this way? Must I drill through the transom? Are there any other viable options?

Thanks!

 

[cpubud]

Re: Bilge pump installation: question regarding outflow

dumping it out the side is fine.keep it above the water line ,and either put a loop in the line or run the line up hill then down to the dump point.

 

[Mark42]

Re: Bilge pump installation: question regarding outflow

This is where I put the thru-hull for the bilge pump on my boat. In fact, I did this today. Its high enough to avoid having water splash into it, but low enough that the hose can run uphill from the thru-hull then down to the pump. Helps keep water out of the bilge.

This is an Attwood investment cast solid stainless steel thru-hull. Well worth the price. And it has a recess cut in the back side so it will hold sealer against the hull for optimum sealing.

The swim platform is visible in the photo, and its above the water when the boat is at rest.

 

[scoutabout]

Re: Bilge pump installation: question regarding outflow

That's a nice, clean install, Mark. I like.

One other factor to consider when purchasing and installing a pump axesligner, is the concept of bilge pump "lift". That is, the gph rating on the box is not real-world performance.

From BoatReports.com...

"...the question of ?lift? is important. Manufacturers rate their pumps for zero lift. It?s called ?open flow? or ?open bucket.? It just means that the water intake, discharge and pump are in a horizontal line. They often include the ?open flow? rating in the pump?s name.
The ratings serve only for comparison. When lift is introduced, few pumps will produce their ?open flow? ratings."

Most installs will result in at least a foot or two of lift from the bilge to an outlet such as Mark has installed -- more if you are going up over the side.

I've read that efficiency losses through lift or sometimes referred to as head pressure, coupled with voltage losses can mean real world performance will be significantly less.

One other thing to consider is using smooth-walled tubing versus the corrugated stuff -- less flow turbulance, therefore less resistance, and hopefully, more performance.

 

[Mark42]

Re: Bilge pump installation: question regarding outflow

That's a nice, clean install, Mark. I like.

One other factor to consider when purchasing and installing a pump axesligner, is the concept of bilge pump "lift". That is, the gph rating on the box is not real-world performance.

From BoatReports.com...

"...the question of ?lift? is important. Manufacturers rate their pumps for zero lift. It?s called ?open flow? or ?open bucket.? It just means that the water intake, discharge and pump are in a horizontal line. They often include the ?open flow? rating in the pump?s name.
The ratings serve only for comparison. When lift is introduced, few pumps will produce their ?open flow? ratings."

Most installs will result in at least a foot or two of lift from the bilge to an outlet such as Mark has installed -- more if you are going up over the side.

I've read that efficiency losses through lift or sometimes referred to as head pressure, coupled with voltage losses can mean real world performance will be significantly less.

One other thing to consider is using smooth-walled tubing versus the corrugated stuff -- less flow turbulance, therefore less resistance, and hopefully, more performance.

I just got back from the hardware store. Bought the clear plastic smooth wall tube and a couple of barbed poly elbows. The corrugated hose that comes with those "install kits" have a real impact on flow due to the resistance caused by the corrugation of the hose.

TD and others mentioned using the clear hose, so at $0.79 a foot, its worth a try. Nice and smooth, it should perform well, but the 2 or 3 90* elbows that it will need will add back some restriction to the flow. Hopefully not as bad as using the corrugated hose.

The hose will run around the fuel tank, so two 90 elbows are needed to keep the hose from collapsing at the sharp bend.

I'll post some pics when done later today.

edit -
BTW, if the thru-hull is 18 inches above the pump, but the hose loops up to 25 inches above the pump before connecting to the thru-hull, the pump is only feeling a 18 in lift, not a 25 inch lift. (it feels the 25 in lift on start up, but once the water starts back down hill to the thru-hull, the siphon effect reduced the actual lift on the pump)

 

[axeslinger1957]

Re: Bilge pump installation: question regarding outflow

Thanks, all! This is giving me the meaty info I had hoped for! Next question: how big a pump do I need to get this done? I can get my hands on a 500 gal/hr, a 600 gal/hr and I think a 100 gal/hr quickly? Is one of these enough?

 

[Mark42]

Re: Bilge pump installation: question regarding outflow

Thanks, all! This is giving me the meaty info I had hoped for! Next question: how big a pump do I need to get this done? I can get my hands on a 500 gal/hr, a 600 gal/hr and I think a 100 gal/hr quickly? Is one of these enough?

Size of pump is based on the size of the boat. Most manufacturers make recommendations for GPH flow for different boat lengths. I use a 750 gph pump that is plenty big for my 16 footer.

Keep in mind that the pumps main function is to remove water from minor leaks, rain and big waves, etc. Its not going to save you when a 4x4 post or 6" diameter log punches a hole in the hull when struck at 60 mph.

Here is an interesting article on bilge pumps that everyone should read. It has an interesting take on bilge pump sizing that basically contradicts the "bigger boat needs bigger pump" mindset:

http://seagrant.uaf.edu/bookstore/boatkeeper/bilge-pumps.pdf

This is what I got done today on my own bilge pump install....

Before:

After:

 

[triumphrick]

Re: Bilge pump installation: question regarding outflow

Looks good Mark. Now may be the time to discuss the covering of electrical connections with shrink sleeve tubing, found at the local Radio hut or Big Box. It can be shrunk using a hair dryer, but for around $12 Harbor Ft. has them. 2 speed if not mistaken. Many an electrical failure has occurred down in the bilge due to the connections not being made correctly!

 

[axeslinger1957]

Calling Mark42!

Calling Mark42!

This is what I got done today on my own bilge pump install....

Mark:

You got that tubing at the local hardware for less than a dollar a foot?
Is that the thin-walled stuff? My microscopic local hardware has clear tubing that is 1/8 inch thick for about $2.00 a foot -- but not in the size I need for my pump. Any ideas?

 

[Gary H NC]

Re: Bilge pump installation: question regarding outflow

Looks like Mark used the shrink type connectors....

I like the liquid electrical tape too....
Nice job Mark...

 

[Mark42]

Re: Calling Mark42!

Re: Calling Mark42!

Mark:

You got that tubing at the local hardware for less than a dollar a foot?
Is that the thin-walled stuff? My microscopic local hardware has clear tubing that is 1/8 inch thick for about $2.00 a foot -- but not in the size I need for my pump. Any ideas?

Home Depot and Lowes carry the clear plastic hose too. Others have used auto heater hose. The problem with both of these hoses is they kink on tight bends, so its better to use the poly fittings when making tight bends. Yes, the fittings will cause a little restriction at the bend, but not as much as a kinked hose!!!!

 

[Mark42]

Re: Bilge pump installation: question regarding outflow

Looks like Mark used the shrink type connectors....

I like the liquid electrical tape too....
Nice job Mark...

Actually, I packed the crimps with boatlife seal after crimping. And a little dielectric grease in the connecters too. I did get some peel and stick tabs that attach to the tank to hold the wires up. They really shouldn't get wet up there.