Six volt bilge pump

[billy-j]

I have a 1956 Lyman wood boat and a 1956 Johnson 30 HP. 6 volt electric start.I want to keep the boat period correct with the six volt system. I would like to get a 6 volt bilge pump for this boat if possible anyone have a source? Bill,

[legendre]

Can’t help you with a 6V pump, but for around $20-$25 you get buy a high-efficiency DC-DC boost converter that will let you run a 12V pump on your 6V system. They typically take 3V-12V input, and have a fixed output voltage (you’d want 12.6V) or a user-set output voltage in the 6-35V range, and are neither very large nor heavy.

Conversion efficiency is in the 90-95% range. Be sure to get a unit that has a current rating 50% greater than the typical load of your pump, and it should be smooth going.

ETA: Once you have stable 12V on-tap, you can do all kinds of nice stuff like charge a phone or tablet, run a little 120V inverter, what have you. Heck, use it to keep a little 12V sealed gelcell topped-up.. the converter will appreciate the battery, if the pump jams or otherwise overloads.

[legendre]

eBay item #171122662244 is 6V-40V @ 15A input / 8V-80V @ 10A output. The limit here will be the 15A input max, which limits total output power to ~90W. But 90W will easily power a typical 12V pump that draws 4-5A (60W).

$20 shipped.

[outboard315]

So the first question is how well does a standard 12v pump run on 6 volts. Second is how well does the johnson run on the 6 volt system. I have heard old 6 volt tractors using an 8 volt battery that you can charge with the standard charger and let’s the ignition and starter work better, that may let you run the 12 volt pump.

[legendre]

quote Outboard315:

So the first question is how well does a standard 12v pump run on 6 volts.

In all likelihood, similar to how well a 12V light bulb runs on 6V.. dim & crappy at best. Recall that in +most+ applications, power squares with voltage – so cutting a 12V device down to 6V will supply it only one-quarter of the power it had at 12V.

He is best off either locating and using a 6V pump, or purchasing a boost converter and running a modern 12V pump. I’d prefer the former, if at all possible.. but the later also has its charms, like having 12V on-tap for all kinds of other uses.

BTW, how does an 8V lead-acid battery work? They are 1.5V per cell, so you can get 6V, 7.5V or 9V – but not 8V per se. Perhaps those "8V" batteries are actually 5-cell units with 7.5V?

[billy-j]

Legendre, I looked at eBay item # 171122662244 what does the 15 amp input max mean? my 6 volt battery is hundreds of amps starting power would not the battery just burn this up instantly? I looked at other converters on eBay there really is not any others that go from 6 to 12. But for the 12 volt there are plenty to go up 18 24 36 volt or from these three down to 12. I am now thinking a 12 volt bilge pump uses about 2 amps to run. If maybe a small 12 volt rechargeable battery from say a kids power wheels might do the job powering a bilge pump. I have run my 6 volt starter on 12 volts in the past and I know it probably does not hurt it but after restoring my 56 Johnson 30 HP. I like to operate it like it was done in 1956. The boat is small only 15 feet long and i have to watch the weight of what I am carrying so two full size battery’s are out of the question. Bill,

[legendre]

Howdy Billy,

quote Billy J:

Legendre, I looked at eBay item # 171122662244 what does the 15 amp input max mean?

It means exactly what it sounds like.. Regardless of how much power you’re pulling from the output, the input cannot cope with more than 15A continuous input current. If your output load causes the input to exceed 15A, then the boost module will either shut down -or- suffer damage, if it lacks protection measures.

More than likely, it +does+ have protection and will simply limit the output, if that’s what you subject it to.

quote :

my 6 volt battery is hundreds of amps starting power would not the battery just burn this up instantly?

No. Current capacity rating is an upper limit – if you have a supply / battery that’s rated for "100 Amps", that doesn’t mean it will supply 100 Amps all the time. It means that when you load it down, it can supply up to 100 Amps when asked to do so.

quote :

I looked at other converters on eBay there really is not any others that go from 6 to 12. But for the 12 volt there are plenty to go up 18 24 36 volt or from these three down to 12.

That’s just what’s being offered on eBay, there are plenty of other devices on the market. But so long as the input will take 6V, and the output will supply 12V, you will be just fine.

quote :

I am now thinking a 12 volt bilge pump uses about 2 amps to run.

I’ve done a little looking, and it seems that basic bilge pumps (12V types) use between 2 Amps and 5 Amps. 12V @ 5 amps is 60 Watts.

quote :

If maybe a small 12 volt rechargeable battery from say a kids power wheels might do the job powering a bilge pump.

Maybe, but it will discharge pretty quickly.. and need to be recharged right away, from a source on the shore.. unless you’ve got a converter on-board.

quote :

I have run my 6 volt starter on 12 volts in the past and I know it probably does not hurt it (…)

Running a 6V starter from a 12V battery is +brutal abuse+. You’re forcing that starter motor to swallow nearly FOUR TIMES the power it was meant to.. and while it may start your motor fairly quickly, it’s going to cause serious overheating and damage (to the starter) in very short order, if you continue to crank it. That’s a last-ditch dire circumstance option.. don’t do it unless it’s absolutely necessary.

[wiscoboater]

When I was a kid I had an old Johnson 35 with the 6 volt system. Being young and dumb, I used a 12 volt battery with it. It lasted about a week. I had the cover off the motor out in the middle of the lake where the boat died. Trying to restart it, the starter gear and related parts grenaded into multiple pieces. I can still hear the parts hitting the water one at a time… plop…plop…plop.. and at the same time realizing I had no oars with me.

[legendre]

quote wannabe outboard guy:

When I was a kid I had an old Johnson 35 with the 6 volt system. Being young and dumb, I used a 12 volt battery with it. It lasted about a week. I had the cover off the motor out in the middle of the lake where the boat died. Trying to restart it, the starter gear and related parts grenaded into multiple pieces. I can still hear the parts hitting the water one at a time… plop…plop…plop.. and at the same time realizing I had no oars with me.

A 300W starter doing 1200W? Nah, what could go wrong? 😆

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