Need a 12V Choke Solenoid

[lmsmith]

So my motor, 1956 Evinrude 30hp, is a 6 volt motor and I would like to convert it to 12 volt. I'm shopping for a 12 volt choke solenoid and I'm a little shocked at the price for one, $140, http://www.marineengine.com/parts/vintage-evinrude-johnson/ITEM_2836/catalog.html?http://www.marineengine.com/parts/vintage-evinrude-johnson/ITEM_2836/ITEM_283600001.htm The link is for a 1957 35 hp, but I thought it would work becuase they are the 12 volt variety.

Is the price correct? Is there a better price? Are there other options? For that price I think it might be better to just go 6V and use what's there.

Now that I think about it I may posted int he wrong spot, I probably should have put it in electrical. Mods if you agree please move.

 

[Lyle29464]

Re: Need a 12V Choke Solenoid

add a resistor

 

[F_R]

Re: Need a 12V Choke Solenoid

add a resistor

Exactly. Go to an auto parts store and get an ignition resistor. They were used on many old cars. I'm not a car expert, so I can't give you a list. I'd take a stab at it and guess a '58 Chevy (Delco).

Connect the choke wire to one end of the resistor, and connect the other end of the resistor to the 6V choke solenoid. The resistor drops the 12V down to 6V.

 

[lindy46]

Re: Need a 12V Choke Solenoid

Or check Ebay or go to AOMCI.org classifieds and post a want-ad. You should be able to find a good used on for $15-30.

 

[cocotower]

Re: Need a 12V Choke Solenoid

Exactly. Go to an auto parts store and get an ignition resistor. They were used on many old cars. I'm not a car expert, so I can't give you a list. I'd take a stab at it and guess a '58 Chevy (Delco).

Connect the choke wire to one end of the resistor, and connect the other end of the resistor to the 6V choke solenoid. The resistor drops the 12V down to 6V.

A resistor reduces current, not voltage. I'm sure that the choke solenoid is still getting 12v but less current based on the value of the resistor.

 

[tx1961whaler]

Re: Need a 12V Choke Solenoid

A resistor reduces current, not voltage. I'm sure that the choke solenoid is still getting 12v but less current based on the value of the resistor.

V=IR
The resistor drops voltage across it proportional to the current going through it. The only time a resistor has no voltage drop is when there is no current going through it.

 

[F_R]

Re: Need a 12V Choke Solenoid

Check your facts. It is Elementary Electricity 101. Current is determined by the source voltage divided by the TOTAL resistance in the circuit. In this case, resistance of the added resistor, plus resistance of the solenoid coil. So, yes it does reduce the current. But the rest of the story is that it does that by dropping the voltage across each resistance. The TOTAL voltage drops across all resistances in a circuit always equals the source voltage. Assuming the solenoid and resistor are equal in resistance, there will be an equal voltage drop across each item. In other words, there will be a 6V drop across the resistor, and a 6V drop across the solenoid. The solenoid is "seeing" 6V and the resistor is "seeing" 6V.

 

[HighTrim]

Re: Need a 12V Choke Solenoid

The starter is fine on the 12V system, but that solenoid will fry if it is held on for a substantial time. Especially since the choke is usually used to shut her down if you havent added a kill circuit. (which is a good idea by the way)

If you need the original 6V wiring diagram, and the 12V modification wiring diagram PM me.

I wish I knew the solenoids were worth that much, Ive been selling them for 5 bucks, lol

 

[HighTrim]

Re: Need a 12V Choke Solenoid

add a resistor

I have never tried the resisitor, I did shop for one once but the kid at the parts counter did not seem to know what I was talking about and couldnt search without a parts number. The second parts store I tried their system only went back to the later 60s.

Anyone actually bought one and know what they bought? Id like to get one.

 

[F_R]

Re: Need a 12V Choke Solenoid

For Pete's sake, here: http://www.ebay.com/itm/Standard-Tr...pt=Motors_Car_Truck_Parts_Accessories&vxp=mtr

Don't know if they will ship to Canada, but at least they give you page after page of applications you can go to your local jerk with.

 

[wilde1j]

Re: Need a 12V Choke Solenoid

There are tons of these on EbAY ... SEARCH "ignition ballast resistor" including a bunch for Chrysler and GM products.

 

[HighTrim]

Re: Need a 12V Choke Solenoid

Thanks.

I was given this by a fellow AOMCI member for those looking for the same.

AC Delco Part #C1101 or Part #U1745

 

[HighTrim]

Re: Need a 12V Choke Solenoid

There are tons of these on EbAY ... SEARCH "ignition ballast resistor" including a bunch for Chrysler and GM products.

I saw how many came up before and did not know how to tell the ones that were for 6V to 12V

 

[Chris1956]

Re: Need a 12V Choke Solenoid

Gee, Don't you need to know the current draw of the solenoid before you can choose an appropriate resistor?

 

[F_R]

Re: Need a 12V Choke Solenoid

You need to know the RESISTANCE of the solenoid. You can measure that if you are doubtful. Hey, this isn't rocket science. Who cares if you get 5V or 7V at the choke when it is all said and done? It will be good enough.

EDIT: "Assuming" there is one ohm resistance across the solenoid and you add an one ohm resistance, the total resistance is 2 ohms. Using Ohm's Law, i=e/r; i=12/2; i=6amps. We already know that the resistances are equal so the voltage drops will be equal across each, and add up to the source voltage, in other words 6V across each.

OK, complicate it a bit. "Assuming" the reistance across the solenoid is double that, or two ohms. Now we have a resistance of one ohm in the resistor + two ohms in the solenoid, total 3 ohms. Back to Ohm's Law, 12/3=4 amps. A known rule says that the current is the same through each part of the circuit. Again using the Law for voltage, e-ir, e=4*2=8V across the solenoid, and e=4*1=4V across the resistor. See, 4volts drop across the resistor, plus 8volts drop across the solenoid equals the source voltage (12V)

Ohm's Law: E=ir or i=e/r or r=e/i "i" is current, measured in amps. "e" is electromotive force, measured in volts, and "r" is resistance, measured in ohms.

No voo-doo, just math. It all started at the time of Creation. But that's another story.

 

[Chris1956]

Re: Need a 12V Choke Solenoid

F_R, How do you choose the wattage of the resistor? Do you need a wire wound one?

 

[wilde1j]

Re: Need a 12V Choke Solenoid

All the ignition ballast resistors have adequate capacity to handle a choke solenoid and all I've seen appear to be wire wound. You're overthinking this.

 

[F_R]

Re: Need a 12V Choke Solenoid

F_R, How do you choose the wattage of the resistor? Do you need a wire wound one?

That is a valid question. But as wilde1 says, don't worry about it if using an ignition resistor. On the other hand, a little quarter watt carbon resistor from Radio Shack won't be enough. If you want to persue the question, you need to measure the resistance of the solenoid and your proposed resistor, then calculate the current as I described above. Once you know the current, multiply that figure by the voltage (12) to arrive at watts. Chose a resistor with at least that high a wattage rating, or more.

EDIT: Oops, lessee, that isn't right is it? Once you know the current, calculate the voltage drop across the resistor, then multiply that number by the current to get watts for the resistor. Is that right??? Now I'm getting confused. Must be a senior moment.

 

[Chris1956]

Re: Need a 12V Choke Solenoid

F_R, Thanks for the council. I am trying to bring some electrical engineering into the discussion, as what the OP is trying to do has not been done so many times that the solution is widely known. I also like answers based upon analysis. In my profession, if there is no analysis supporting a claim, we consider it to be marketing....

 

[wilde1j]

Re: Need a 12V Choke Solenoid

F_R, you are quite correct: Calculate Watts. To calculate the circuit power... The formula is W = V x I


The problem in attempting to 'engineer' this is lack of data, given the ignition ballast resistor is likely the best and most practical solution. Just try to find the power rating of one of these!