75 20hp ignition troubles

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hawk-eye

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Hey guys, Ive been tryin to troubleshoot this engine for lack of spark. I figure Ill take some mesurements and ask for opinions.

its a 1975 evinrude 20 hp Model #205B62BC.
Finding info and parts for this guy has been a challenge.

In the Photo the driver coil circled in yellow supplies both spark coils.
out of that I got
accross the 2 wires 1.1 ohm
Blue to ground 0.4 ohm
Blue and White to ground 0.4 ohm

Coil circled in green
Blue to Spark lead 12.4 Kohm
Blue to ground 1.3 ohm
Spark lead to ground 12.4 Kohm

Coil Circled in blue
Blue and white to spark lead 12.35 Kohm
Blue and white to ground 1.3 ohm
spark lead to ground 12.35 kohm

IMG_70162.jpg


Coil circled in red is for the ac power outlet, i didnt test it, i dissconected it.
 
bktheking

bktheking

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Re: 75 20hp ignition troubles

Did you disconnect the leads going to the stop switch to test first?
 
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hawk-eye

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Re: 75 20hp ignition troubles

Any ideas where I can find a parts catalog online for this motor? BRP dont have this one on there site.
 
bktheking

bktheking

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Re: 75 20hp ignition troubles

Sure they do, shop.evinrude.com. This is a low tension magneto setup. The driver coil under the flywheel generates the voltage for the breakers which feed the 2 external coils.

The driver coil- should read .75-.95 ohms, either lead to ground with meter set on the high side should read infinity, you are getting .4. I suspect your driver coil is kaput.
 
bktheking

bktheking

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Re: 75 20hp ignition troubles

PS- i think you have the driver and lighting coils reversed, I believe the driver is the light green, the lighting is the dark one, they arent reversed on your engine, your colour reference is wrong. If you didnt test the light green one you should.
 
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hawk-eye

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Re: 75 20hp ignition troubles

The coil in yellow has a blue, and a blue and white lead comming out. \the coil in red has a yellow, and yellow and black comming out.
I was kinda hoping you would tell me the driver is not reading right. Is the lighting coil the same as the driver coil? I cant find the part number to cross referance it? I will go test the lighting coil as well.
This engine has not run since 1993, I got it from my grandfather who bought it new in 75 and only used it once a year for a fishing trip till 93.
 
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hawk-eye

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Re: 75 20hp ignition troubles

Well i tested the lighting coil
yellow to yellow .09 ohm
yellow to ground 300 kohm
yellow to ground 300 kohm
 
bktheking

bktheking

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Re: 75 20hp ignition troubles

Well the blue and blue white is the driver, yellow would be AC lightening coil. Its strange as the diagram shows the coil closest to the head as being the driver coil. I woudnt try swapping them if I were you, id get the proper driver coil.

PS- you can tell its in good shape.
 
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hawk-eye

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Re: 75 20hp ignition troubles

bktheking said:
Sure they do, shop.evinrude.com.
Click to expand...

I swear this engine dose not exist. shop.evinrude.com don't have a listing for this motor, nor dose anyone else. Ive been using that site to get internal parts for it but ive been using the listing for 1973 18hp. Im not sure if I trust ordering electrical parts the same way. I cant find another motor diagram with ac lighting option.

If the lighting coil is the same as the driver coil I can try and swap them, but Ill hold out for some confermation before I try it.
 
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hawk-eye

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Re: 75 20hp ignition troubles

Thanks for the help bktheking, hows the weather in your end of Ontario, it was 21 deg and dry here in Woodstock today.

Did you find the diagram for this engine? or one similar? Id like to see it, seems to be a lot of guess work for these old Canadian engines.
 
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hawk-eye

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Re: 75 20hp ignition troubles

I would like to find the part number of the lighting coil, if anyone knows where I can find it?
 
bktheking

bktheking

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Re: 75 20hp ignition troubles

lookup 73 johnson 20 hp, I dont see a 75
 
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hawk-eye

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Re: 75 20hp ignition troubles

samo_ott said:
BTW, are you sure on the year/model as I do not see anywhere that OMC made a 20 hp in '75.
Click to expand...

Yeah Im sure, I cant find anything about 75 20hp either. From what I understand it was only available in the Canadian market.

I thank you guys for your help.

I have ordered the new driver coil, and also a point kit with condensers.

I am trying to find a wiring diagram of the terminal block. The only thing using it is the lighting coil. Just want to make sure that its set up right. There is 2 yellow wires comming from the coil to the terminal block and only one from the block to the outlet. Im just not sure what to do with the other.

Thanks guys.
 
samo_ott

samo_ott

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Re: 75 20hp ignition troubles

I'm in Canada and sure don't see it listed. I would recheck your model #.
 
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hawk-eye

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Re: 75 20hp ignition troubles

Well I finally have some time to look at this old girl again.

Is is possible for the ignition coils to read resistance ok but still fail when a load is applied?

PS One of the blue coils has a crack in the housing, and I am quite sure they are origional from 1975.
 
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