bilge pump voltage question

[jim rosenthal]

Many years ago, I added a Jabsco diaphragm pump to the bilge pump array in my Hatteras. All the other pumps ever on the boat were centrifugal pumps, which will not strip the bilge dry, as they will not generate suction. The Jabsco pump, which was the largest they made, with 1" inlet and outlet pipes, is in the head locker and strips the bilge dry using an extension hose and a small bronze strainer. I didn't need such a large diaphragm pump, but since I found a brand-new one in a boating flea market, I used that one.

I installed that pump in the boat about twelve or fifteen years ago. Recently it stopped working. It still spins, but doesn't pump. More than likely, there is a hole in the diaphragm or a valve is fouled. These pumps are rebuildable, so as soon as I can get it out of the boat I am going to do that. Jabsco no longer builds these pumps, but they do sell all the rebuild kit parts as well as new motors for them.

The failure of the pump prompted me to look around on line (that's how I found out they don't make the largest one anymore) I did find a brand-new one on Craig's List in Norfolk, and since I have kids down there, I sent one over to buy it and picked it up from him on my next trip down there. And, sure enough, it's a brand new Jabsco 24600 pump. But it's 24 volt, and my boat is 12v.

Here's my question (and I can buy a 12v motor for it and swap it in, so this is mostly a matter of curiosity): if I run a 24v pump on 12v, will it just run slower? will it overheat? will it not run at all? Maybe one of our many marine electricians can enlighten me. I would imagine it would just run slower- but I'd like to know.

 

[Boatsb]

Many years ago, I added a Jabsco diaphragm pump to the bilge pump array in my Hatteras. All the other pumps ever on the boat were centrifugal pumps, which will not strip the bilge dry, as they will not generate suction. The Jabsco pump, which was the largest they made, with 1" inlet and outlet pipes, is in the head locker and strips the bilge dry using an extension hose and a small bronze strainer. I didn't need such a large diaphragm pump, but since I found a brand-new one in a boating flea market, I used that one.

I installed that pump in the boat about twelve or fifteen years ago. Recently it stopped working. It still spins, but doesn't pump. More than likely, there is a hole in the diaphragm or a valve is fouled. These pumps are rebuildable, so as soon as I can get it out of the boat I am going to do that. Jabsco no longer builds these pumps, but they do sell all the rebuild kit parts as well as new motors for them.

The failure of the pump prompted me to look around on line (that's how I found out they don't make the largest one anymore) I did find a brand-new one on Craig's List in Norfolk, and since I have kids down there, I sent one over to buy it and picked it up from him on my next trip down there. And, sure enough, it's a brand new Jabsco 24600 pump. But it's 24 volt, and my boat is 12v.

Here's my question (and I can buy a 12v motor for it and swap it in, so this is mostly a matter of curiosity): if I run a 24v pump on 12v, will it just run slower? will it overheat? will it not run at all? Maybe one of our many marine electricians can enlighten me. I would imagine it would just run slower- but I'd like to know.

I'm sure someone will tell me I'm wrong but running 12 v to a 24v motor will not work. It may turn slowly if at all but that is not a good plan. Try reading the original post where it said rebuild kits and replacement motors are still available. A quick motor swap should be easy.

 

[chris piazza]

Not sure Jim but I would think that running 12v to 24v motor would be like trying to run one of your AC units on 60v instead of 120v, it may work but any electric motor draws the most amps at start up

Chris
Superior Nights 53C

 

[jim rosenthal]

Duly noted. Motors are available. I will change the motor out for a 12v one.

I hope they make the brass spigots that the hoses clamp onto. They were so corroded by years of use that they broke off. So it's good that it came out now rather than later.

 

[jim rosenthal]

I rebuilt the Jabsco pump on the dining room table this evening. The brass spigots are only available if you purchase the entire replacement pump base, which is +$300, and NLA at most places. Since everything else on the pump is perfectly good, I ordered a one foot piece of 1" copper pipe from McMaster-Carr, and I will make two new spigots from that. The brass pieces that came in the original pump crumbled from salt water exposure, I think. They lasted fifteen years in there, can't complain on that. I'm also ordering a 12v motor for the new pump I found on line. If anyone needs a 24v motor for the large Jabsco diaphragm pump, let me know. You'll get it cheaply.

 

[bostonhatteras]

Is the new 12v motor less money than having the 24 v motor armature rewound to work on 12v? Or rewinding it would give you a 12v spare motor.

 

[tonytrakovich]

Jim,

To answer your question- Unlike AC motors, DC motors use voltage to regulate speed. An unloaded 24V motor will run half as fast on 12V. This is basically how the blower motor for your car heater works. The only problem would be if your load caused motor to stall. In that case the motor will start to draw too much current (amps) and burn out.

AC motors are induction motors and basically rely on frequency to regulate speed. Low voltage under load will generate excessive heat and burn it up.

I think it was wise to just change the motor to have piece of mind that if you need it, the bilge pump will work to rated potential.