changing the starter system on a big twin 25

todd281

Petty Officer 2nd Class
Joined
Jan 21, 2015
Messages
159
I own a 1954 Evinrude Big Twin 25 model 25916. When Evinrude changed the electric system from 6 volts to 12 volts, did they change the starter mounting bracket? My system is 6 volts [with a bad starter] and I want to change it to 12. I bought a new 12 volt starter, that I am told is the replacement , but it will not fit the bracket. I am trying to find out if I have the wrong bracket, or the wrong starter. The bracket I have has part # 303729
 
Last edited:

boobie

Supreme Mariner
Joined
Nov 5, 2009
Messages
20,826
I believed they changed the bracket 'cause the six volt was bigger. But I may be wrong.
 

F_R

Supreme Mariner
Joined
Jul 7, 2006
Messages
28,195
Yes, the bracket is different. For one thing, the hole spacing is different where the starter bolts up.
 

gm280

Supreme Mariner
Joined
Jun 26, 2011
Messages
14,585
Looks like if you can't find something in an earlier model that will fix, you may need to design something to work...
 

F_R

Supreme Mariner
Joined
Jul 7, 2006
Messages
28,195
To the best of my knowledge, a 1957-up 35-hp bracket will work. But I can't say that I've ever personally done it on a '54.
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
I have a feeling you would be in the same boat with a 6 volt bracket.If youi have it on hand give it a look.
 

F_R

Supreme Mariner
Joined
Jul 7, 2006
Messages
28,195
I just checked the parts book, and a 22DE14LE is a 6 volt system. So, as steelspike said..............
 

todd281

Petty Officer 2nd Class
Joined
Jan 21, 2015
Messages
159
Sorry for the late reply ,I have been away from my pc all week. I ended up taking a chance, and bought one from a '57 model . It is a different bracket, in that the starter bolts are closer together than, on the six volt model. It does bolt to the powerhead just fine. the only other difference that I see is the rubberized mount for the engine cover, which is on the '54 six volt bracket, is not on the newer 12 volt one. I think it will be easy enough to fab one for it. Now I just have to locate a 12v choke solenoid and find the room under the cover for a starter solenoid ,some paint, decals, and the fish... thanks for the replies
 

F_R

Supreme Mariner
Joined
Jul 7, 2006
Messages
28,195
Do you have the original 6V choke solenoid? If you do, would you do a lot of people a favor and take a digital voltmeter (multimeter) and measure the resistance of the solenoid winding? I have been asking for this information for some time now, and nobody seems to care. With that number, I can pick the ideal series resistor to insert and continue to use the 6V choke on 12V.
 

nwcove

Admiral
Joined
May 16, 2011
Messages
6,293
Frank, i just checked the choke solenoid on the elto, with the meter set on the 200 ohm scale, it read 3.3.
 

F_R

Supreme Mariner
Joined
Jul 7, 2006
Messages
28,195
Thank you for that information. I started researching this subject some time ago, and with this information maybe we can get somewhere. Now I need to find my notes............wherever the heck I put them. Bottom line is that inserting a 3.3 ohm resistor in line with the solenoid will drop the 12V input to 6V. I'll get back on this later, after Church.
 

todd281

Petty Officer 2nd Class
Joined
Jan 21, 2015
Messages
159
Thank you for the info on the 3.3 ohm resistor. I have been looking at replacing the solenoid with a 12 volt one, but it will be a lot cheaper, I think, to get a resistor. You wouldn't know off-hand what amp rating? I mounted the starter , and a simple mod for the cover bracket, ended up finding room for the starter solenoid right on the bottom of the starter. Thanks again,
 
Last edited:

F_R

Supreme Mariner
Joined
Jul 7, 2006
Messages
28,195
Ok,, first let me clarify, we are talking about the choke solenoid here, not the starter solenoid. Having said that, I am somewhat surprised at the numbers, and my list of possible resistors just went out the window. So, let's start over.

Resistors are rated and sold by two basic values, Resistance and Wattage. To find the wattage in our choke circuit, we first need to find the current (in Amps). To do that, we use Ohm's Law. It says Current equals Volts divided by resistance. We know the Volts is 12. To find the Resistance, we need to add the resistance of the solenoid, plus the resistance of our added resistor. So, 3.3 + 3.3 = 6.6 ohms. Now we can apply that to Ohms Law. 12 Volts divided by 6.6 Ohms = 1.818 or rounded off to 1.82 Amps..

Now that we know the current, we can find the Watts. Watts equal Volts times Amps. So, our 12 Volts in our example are divided equally between the resistor and solenoid. 6V at the solenoid and 6V at the resistor. 6V times 1.82 Amps = 10.9 or rounded off to 11 Watts. I gotta admit, I'm kind of surprised at that. But anyhow, we now know that our choice of resistors ideally should be 3.3 Ohms and 11 Watts. More Watts' rating is OK, but not less.

Now comes the search. Suppose we can find a 3 Ohms resistor but not at 3.3 We can calculate the resulting voltage at the solenoid by using the above calculations. Total resistance becomes 3.3 for the solenoid + 3 for the resistor = 6.3. 12V divided by 6.3 = 1.9 Amps. The Watts will be a hair more than before, due to the increase in Amps.

So, question becomes what would be the resulting Voltage at the solenoid. Back to Ohm's Law, we know that Volts equal Current times Resistance. We also know that the resistance across the solenoid is 3.3 Ohms. Multiply 3.3 Ohms times current (1.9 Amps) and we get 6.27 or rounded off to 6.3 Volts across the solenoid. That makes a 3 Ohm 12 Watt (or more) resistor well within tolerance.

In the real world, we will probably be purchasing a 50 Watt resistor. As I said, more is better, less is not.

Hope somebody is able to wade through this and understand.

EDIT: I already had to make some corrections to this. I hope I got it right this time.

EDIT, EDIT: Radio Shack has a resistor 3.9 Ohm, 10W resistor item Model: NTE 10W3D9, Catalog #: 55047899 for $1.21 (On-Line only). I haven't calculated the numbers, but for a buck-twenty one, I'd be tempted to try it. The voltage at the solenoid will be less, but if it works reliably, OK. Let us know the results if you do try it.
 
Last edited:

todd281

Petty Officer 2nd Class
Joined
Jan 21, 2015
Messages
159
WOW.. F_R, I have to say I'm impressed. I just searched for a resistor and have 2 choices. a" 3.3 ohm, 3.3R, 50 watt" or a "3.3 ohm 25 watt" The price on them are about the same. [I have no idea what the "3.3 R" stands for] So which one do you think? Thanks so much for all the help on this .
 

F_R

Supreme Mariner
Joined
Jul 7, 2006
Messages
28,195
I don't know what the "R" stands for either. But both are well within your wattage requirements. The 25W will operate a tad hotter than the 50W, but it really isn't a big deal here because you are only holding the choke button down momentarily, not long enough for it to get hot.
 
Top