1976 Johnson 25hp ignition upgrade?

nphilbro

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I picked up this old motor for $80 on a whim just because I needed a 25hp as a kicker and it was in excellent condition, well taken care of, and electric start. The seller couldn't start it because it came off a boat he bought and didn't have a tiller arm- or knowledge of the motor.

I finally brought it back to life today after a thorough cleaning and getting an entire bee hive blown out of the exhaust tube but had forgotten how much I hate the point capacitor ignition. I know it's a long shot, but I have various parts motors around and have a couple '85 15hp with charging stators and was wondering if I could install the entire timing base and CDI ignition system into this motor? I would want to use the existing flywheel which has two opposing magnets. Even if I couldn't use the charging stator, I would love to upgrade it to CDI. I could fab an aluminum bracket to attach the power pack, coils should just bolt on.

Curious if anyone has tried this or of I'm overlooking something- like wrong inner diameter or something. I wouldn't think the point armature offset would have any impact on a CDI.
 

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F_R

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Well, for one thing, the flywheel would have to be changed. As for the rest of it, the armature plate/timer base mounts totally different. Can it be mounted on the '76? I seriously doubt it, however I've never looked into it.
 

nphilbro

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I'm pretty sure it wouldn't work, but the reason I've always liked these motors is the fairly slow evolution in parts and bolt patterns with a lot of backward compatibility. I know it's not always the case but I've been surprised more than a few times.
Are the flywheel magnets spaced differently on the two motors?
 
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nphilbro

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Update: You are correct, F_R, the timing base bolt patterns are completely different. I had no intention of taking the flywheel off again but sheared the woodruff this afternoon so that took care of that issue. Since I still had one of the '85's on the stand without the flywheel it was very simple to unscrew the base and compare.

It would still be nice to get a stronger spark out of the system. I've seen some older motors with two charge coils under the flywheel but don't know how close to capacity those caps are to being fully charged.

In any case, I continued the decarb process, brought it up to 3/4 throttle in the tank for a few minutes at a time off and on, in gear (minus the prop), and little by little was able to run it leaner and lower the idle RPMs to the point it runs as slow as my bulletproof '91 9.9hp Johnson. It's all tuned pretty close to factory spec now which is pretty amazing for a 40yo motor. It looked like I was burning tires in the driveway even before treating with Seafoam but there's less smoke at idle now than from my lawn mower. Compression dropped from 138/134 to 135/133 psi which isn't much but might have just been from the carbon burning off. Flywheel is also properly torqued down now, lol.

Since my primary use for this motor will be trolling offshore for salmon, I'll probably lower the tank mix to 75:1 to save the plugs and rings then if I need to use it as a "get home" motor or get into strong winds or current I can just add more oil to the kicker tank. I don't think the spark is strong enough to open the plug gap beyond the .030 its set at now with the J4's.

I normally run 75:1 on my 9.9 for trolling (also bring to 50:1 if I have to run it hard) and opened the plug gap to about .038 and the plugs never foul, even after 4-6 hours of pulling the downriggers over 3 to 4 days straight. The downside I noticed with the bigger gap is that it can be a little harder to start completely cold (4-8 pulls vs. 2-3).

I'll give it a trial run tomorrow in sheltered waters and see how it does on the boat. I don't feel like hooking up control cables right now so just took the grinder to one of the gear tooth tiller arms I had lying around and shaped it to fit. Works surprisingly well. Steering will be controlled with a bar connected to the main engine so its not going to get much force on it anyway.
 
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hardwater fisherman

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My 76 40hp evinrude has the same ignition as yours. I took some advice from leeroys ramblings as to use NGK sparkplugs. All my other omc motors run fine with champion plugs but the low tension magneto does not have a strong spark. Some people have suggested NGK and they dont foul as easy as the champions. What I have read was to cross reference the plugs and chose one number hotter. I got a smother idle and never stalls.
 

nphilbro

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I couldn't get it to even spark on my tester but it did if I grounded the plugs.

I've probably rebuilt two dozen OMC motors over the last 5 years and 3 of my 4 regular runners I rebuilt (my 175hp Ocean Runner was cherry when I got it). That said, I've only rebuilt two point/cap motors, and vowed never to mess with them again so my knowledge on this aspect is based on little experience. Guys from the boat club and fishing buddies often end up buying my kickers right off my transom when theirs crap out over a long fishing weekend, so I've learned to pack a spare in the truck and never turn down an excellent deal on a builder or good parts motor. I'm too thorough with my rebuilds to make a living at it but it's covered my entire truck/boat fuel bill on couple of seasons.

Anyway, how would a hotter plug work with low tension coils? I thought about that early on but wasn't sure if they would even fire. Plugs are something else I don't really know much about either since I pretty much go by the manuals and those CDI / Optical ignition systems are pretty specific.
 

hardwater fisherman

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That ignition was only used for I think 4 years. From what understand they had problems with plugs fouling too often. And if you look at shop evinrude.com the standard plug is as you mentioned J4J but also it says optional plug UJ81J can be used for special applications. I tried the UL81C plug for my 40hp instead of the L4J and they did foul less. But i have had better luck with the NGK plugs.
 

nphilbro

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HF- do run yours at high speed or spend a lot of time trolling or both? I'd like to see how this works for me as a kicker. My biggest concern, obviously, is fouling the plugs during 1-2 hour trolls. I'll usually pull up the kicker at some point and run 5-15 miles with the main before dropping my set again. I suppose I could run it for a few minutes at mid-throttle after the lines are up before lifting it. I only have a 3 gallon kicker tank to run mix in so would hate to run it empty them x-fer fuel over from the main, then mix while on the water.

I guess if its necessary hot lap it to keep the plugs clean- and this motor serves me well, I could attach a shutoff tee, tap line, and bulb after the water separator to refill the kicker tank. I hate to risk getting fuel on my hands while fishing because it can repel the bite. (But not WD40??? Go figure).

If it becomes obvious this is the wrong motor for a trolling application I'll just put it up for sale or trade. I know there are a lot of freshwater guys looking for good running 20-35hp's around here.
 

F_R

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Those motors had slow speed problems when right out of the box, new. Has to do with the emissions control and elimination of crankcase drains. Plugs may help the situation, but I'm pessimistic over a real cure.
 

hardwater fisherman

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I do not troll with mine much, but if the wind picks up or in heavy current. Too strong for my electric I back troll. In forward it pushes me well over 3mph too fast for walleye. Maybe ok for muskies though.
 
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