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1981 25HP Outboard Ignition Coils

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RenaissanceMan

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Hello,

I inherited a 1981 25hp 2 stroke outboard with the skiff my grandfather built. He kept in really good shape and I’m working to keep the motor running well.

I’ve had some recent troubles with the engine cutting out near idle and eventually the power pack failed. I replaced it with recommended part that is slightly different than the original and it starts up great again. Idle isn’t as bad anymore but with about 1/3 throttle it now starts to cut out. I can get through occasionally to full throttle but that middle speed is a challenge. My next thought was the carburetor, so I rebuilt that but it was very clean inside and no damaged parts.

My next thought is the ignition coils. They have exposed cores and are fairly rusted. Primary resistance is good, nearly 0 ohms. Secondary resistance is 1200ohm on one and 1300ohm on the other. I don’t have a part number or spec to go by but feel like them being close to each other is a good sign.

I went to get new parts recommended for this engine, however the recommended 0584561 part number does not have the same terminal connections and the ones I looked at measured 500ohms on the secondary windings. I found Siera part number 18-5194 at West Marine, but tested those and found secondary winding of 6500ohms.

Before going any further, does anyone have and troubleshooting recommendations for testing my current ignition coils to make sure they are not still good? Photos attached.
 
RenaissanceMan said:
Hello,

I inherited a 1981 25hp 2 stroke outboard with the skiff my grandfather built. He kept in really good shape and I’m working to keep the motor running well.

I’ve had some recent troubles with the engine cutting out near idle and eventually the power pack failed. I replaced it with recommended part that is slightly different than the original and it starts up great again. Idle isn’t as bad anymore but with about 1/3 throttle it now starts to cut out. I can get through occasionally to full throttle but that middle speed is a challenge. My next thought was the carburetor, so I rebuilt that but it was very clean inside and no damaged parts.

My next thought is the ignition coils. They have exposed cores and are fairly rusted. Primary resistance is good, nearly 0 ohms. Secondary resistance is 1200ohm on one and 1300ohm on the other. I don’t have a part number or spec to go by but feel like them being close to each other is a good sign.

I went to get new parts recommended for this engine, however the recommended 0584561 part number does not have the same terminal connections and the ones I looked at measured 500ohms on the secondary windings. I found Siera part number 18-5194 at West Marine, but tested those and found secondary winding of 6500ohms.

Before going any further, does anyone have and troubleshooting recommendations for testing my current ignition coils to make sure they are not still good? Photos attached.
Click to expand...
Just got the new coils, both secondaries measured about 260ohms, way less than I think I was expecting but still can’t find a spec sheet. Gonna try them out this weekend and see how it goes.
 
This is a snippet from the CDI troubleshooting guide, i think I got the right page for your engine to check resistances and stuff.
1729254868198.png
 
chrisgt said:
This is a snippet from the CDI troubleshooting guide, i think I got the right page for your engine to check resistances and stuff.View attachment 33896
Click to expand...
Thank you for this information. This appears to be for the alternator, which is great information and something I’ll probably investigate to refurbish between seasons. I was able to replace the current ignition coils with replacements that looked very similar from eBay. They measured about 260ohms each on the secondary coil but major difference is the encased core for protection. Engine ran great last time is was out, not stalling or cutting out issues!
 
faztbullet said:
That info posted is for timer base and stator ..here is what you need from factory service manual...

View attachment 33897
Click to expand...
This is exactly what I was looking for and confirms my new coils from eBay that measured 260ohms each are within tolerance! I replaced them both and took her out last weekend and had no issues stalling or cutting out. The major difference I see is the new cores are encased opposed to the old ones being exposed, which may have contributed to the issues I was having.
 
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