Wiring

[tpls63]

I was just about to convert my 1956 Johnson 30 to 12V by installing a resistor in the choke solenoid circuit per this diagram (http://forums.iboats.com/forum/engi...-1956-johnson-30-hp-rde-18-12-volt-conversion) when I noted that my starter solenoid only has one small terminal and this wiring diagram shows 2.
Does anyone know if I connect the red wire from the resistor to the single terminal with the starter switch wire or simply not use it?
Thanks

 

[gm280]

tpls63, if your choke solenoid has two terminals, one is from the ignition choke switch and the other is probably for ground. Search the wires attached to the solenoid and see where they go. If you see one going to ground or even back to the negative battery terminals, then you still can change it over. However, remember that the choke solenoid isn't the only thing you need to change. Any other circuit that used 6 volts has to be changed as well. JMHO

 

[sam am I]

I'm with gm on this and also due to only having a one wire starter solenoid that must (as best I can tell) **internally tap off the battery terminal for the solenoid's control coil, either you'll need to switch to a two wire starter solenoid and wire it so both choke and starter solenoid's can share one resistor as seen in your link or use two resistor's for each solenoid as seen below as I assume your system is as shown/wired below with the one wire starter solenoid.

**(Due to the starter solenoid's design of an internal tap to the battery+ terminal for the actuation coil, the additional resistor is added to the low side/ground side to limits current for the proposed 6V to 12V mod)

 

[tpls63]

No Title

Yes, my engine is wired like your drawing sam am I. I was told by lindy46 and F_R that it's OK to run the old 6v starter on 12V as long as I don't crank too long.
Here is the drawing from the link in my question above, it shows 2 wires coming off the right end of the resistor (the blue item). On old cars I've restored there is only one wire on each end, one side goes to the power source and the other to the part, in this case the choke solenoid (through the switch).
I don't understand the two wires off the right side in this drawing, it seems like the red wire from the starter solenoid to the right side of the resistor can be eliminated and I can use my original starter solenoid.

 

[sam am I]

Yes, my engine is wired like your drawing sam am I. I was told by lindy46 and F_R that it's OK to run the old 6v starter on 12V as long as I don't crank too long.

I read that and I suppose that'd be okay but yes, be very careful, she'll heat up, not to mention spin up pretty fast.......

I don't understand the two wires off the right side in this drawing, it seems like the red wire from the starter solenoid to the right side of the resistor can be eliminated and I can use my original starter solenoid.

This might help and assuming ONLY the battery is upgraded to 12V, I numbered the text boxes for further reference if need be cuz I'm not sure we're all on the same page. I'm also assuming you have a start switch on the throttle control that energized the starter solenoid (through the mercury switch)? I'm not too familiar with 50's era Johnson's



The resistor in the pic on the left is able to share the two loads(starter and choke) and can be done due to having a two wire controlled starter solenoid. The pic on the right has to be wired with two resistor's due to having the starter solenoid's positive control wire internally wired to the battery positive in lug therefor the current for the 6V starter solenoid has to be limited in the ground path (note 1a) as depicted. The 6v one wire choke remains the same as the pic on left with limiting the current in the positive path (note 3a)...........

 

[F_R]

Assuming it is an OMC solenoid, the two-wire one as shown in the first picture is a 12V solenoid. No voltage dropping resistor is needed if using that one. I suppose anything is possible, and there may be such a thing as a two-wire 6V solenoid, but I've never seen one.

And then to make things even more complicated, there are the two-wire (Ford) car solenoids. Whole new ball game if you get tricked into trying that one. They are different internally.

 

[tpls63]

No Title

OK sam am I, wiring it per your diagram reduces current from 12V to 6V for both the starter and choke. If I didn't reduce the starter and as long as I don't turn it over too long, the 12V won't hurt the starter? Or is it better to get another resistor and do it right?
Another question, can't I run both circuits through 1 resistor with a one wire starter solenoid?
BTW, Thank you all very much for the responses!!!
Here's a picture of the boat/trailer I'm restoring. 1956 Larson Pla-Boy 14- fiberglass. I ordered a power tilt/trim for it which is the reason for the 12V conversion so I don't have to carry 2 batteries.

 

[sam am I]

If I didn't reduce the starter and as long as I don't turn it over too long, the 12V won't hurt the starter? Or is it better to get another resistor and do it right?

The starter's solenoid? If it's a 6V solenoid and you power it with 12V, it'll get pretty hot in fast order....you could get away with it but for how long??? I'll say "Not forever!!" You could get a 12V two wire marine grade starter solenoid pretty easy and just use a resistor for the choke.

Or better yet, get the 12V two wire marine grade starter solenoid AND get a 12V choke and do away with the resistors all together? Perhaps it's a stock/classic boat thing and that's why the effort to not mod too much?

Another question, can't I run both circuits through 1 resistor with a one wire starter solenoid?

Your stock 6V starter's solenoid actuation coil appears hardwired internally to the battery + terminal (by the drawing anyway) and your boat is wired to actuate it through the series combination of the mercury switch and a throttle switch that when both are closed, they complete a ground to energize the starter's solenoid to start.

Your choke solenoid on the other hand then appears to be frame mounted/grounded type (by the drawing anyway) and uses a positive voltage to actuated it.

I really don't see how to use only one resistor to accommodate both circuits (low side solenoid and high side choke) as they currently exist and as they currently wired in your setup, no........

BTW, Thank you all very much for the responses!!!

You're very welcome

Here's a picture of the boat/trailer I'm restoring. 1956 Larson Pla-Boy 14- fiberglass. I ordered a power tilt/trim for it which is the reason for the 12V conversion so I don't have to carry 2 batteries.

It's beautiful!!! Wow......

 

[sam am I]

Assuming it is an OMC solenoid, the two-wire one as shown in the first picture is a 12V solenoid. No voltage dropping resistor is needed if using that one.

I'm not sure who drew that drawing up on the left but they claimed it needed one as per their drawing, but I agree, if it's 12V then no, a resistor is not needed.

 

[tpls63]

No Title

I'm going to get another resistor and wire it according to sam am I's drawing on the right.
My starter button is on the dash and not the control handle but that shouldn't make any difference.
Here are a couple more pictures. I'll have to modify the mount for the starter solenoid to accommodate another resistor.
Thanks again for the help!!

 

[sam am I]

My starter button is on the dash and not the control handle but that shouldn't make any difference.

Geeesh.......I even read/saw that mounting plate like 12 times looking at those prints. I'll use the age card for that!! No, it'll make no difference where the switch lives.

Here are a couple more pictures. I'll have to modify the mount for the starter solenoid to accommodate another resistor.
Thanks again for the help!!

Sure and the math is using an example

The solenoid uses approx. 3 amps at 6V.......
Need to drop the extra 6V (12V - 6V = 6V) at the 3 amps
Requires then 6V/3A = 2 ohms resistor....
Wattage = V * I = 6V * 3A = 18 Watts

Vishay/Dale makes some nice aesthetically looking gold anodized aluminum cased stuff that can be mounted easily that will also help to dissipate whatever heat...don't suspect that much due to crank/chokes times but..........

 

[gm280]

sam am I, good deal with the math to state the resistance and wattage of a dropping resistor. I was wondering if he knew what size to use. I would find at least a 2 ohm 20 watt myself any probably a little higher wattage. More is better with this resistor wattage.

Another idea tpls63, if you can't find a suitable resistor, you can always use another 6 volt starter solenoid in series to solve the problem. It doesn't have to be connected with the heavy cables from the battery, only the small terminals connected in series. JMHO!

 

[oldboat1]

think I would just use a 6 volt start bat (sm and light -- and cheap).

not sure what the draw is for the t. and t., but a 12v mower battery might be fine for that.