77 115 johnson ignition issue

[John800]

I am helping my grandfather with his boat. He has a 1977 115 hp johnson that runs for a few minutes then when everything gets warmed up it kills due to lack of spark. my methhead cousin replaced something on it ,supposedly, but that disnt solve the issue. one of the mechanics at the local dealership said to replace all the componants, thestator goes out and takes out coils ect, and if you replace the components one at a time you will just wreck your new components. That sounds a bit strange to me, but at this piont, i am not against it if it gets the boat useable for him again. At 81 he doesnt have much interest or patience in getting stuck out on the lake.
Any thoughts on doing the complete system?
any advice or imfo on troubleshooting it?
someone here has to have been down that road.
Are oem parts the best way to go or are there aftermarket options? Maybee an upreade to better quality parts?

[DanUmbarger]

There's only 3 things that would make the motor die from losing spark...stator, pulser coils and the pack. The correct way to check it would be with a CD77 meter...after the motor dies check for pack output...no output ...then check stator output...no output - bad stator...output then check pulser coil output. The flywheel/stator supply the pack with juice and the pulse coils release that juice to the coils....it's not going to be all 4 coils I don't think. Prolly going to be a stator or pack.

[mn808gade]

did you check all four wires for spark? should spark 7/16",stator has a ohm resistance that will prob open up when motor gets warm,and prob be your problem,need ohm meter to read..plastic dripping down from stator? if it was power pack or coils not all spark would disapear.where r you located. b glad to check it for ya. i'm on eastshore Mille Lacs Lake.coupla ways to go, after a few tests.terry 612-390-2474

[John800]

So the replace everything advice came from someone that does not know how to diagnose it? Or did not have the equipment? is there any truth to bad parts wrecking new ones? I fond it really hard to believe.
Would the min max funtion on a fluke meter work? I would think so, or maybe the signal is to fast.

[John800]

Mn808gade, i am near rochester so quite a ways from millelacs but I appreciate the offer. If you dont mimd i may call you if i get out there

[mn808gade]

might have a used stator that will match.post mod#-th

[H2OPERF]

If it is a 77 it should have screw terminals on the power pack in the back,, remove the cover and remove the black wire with a yellow stripe and see what it does.... this is the kill wire so u will not be able to shut it off so have the water hose on and be ready to choke it down or have a wire hooked to ground ready to stick on that terminal to shut it off.. Changing everything is rediculous, like was said above check the stator resistance most likely culprit for heat related problem, trying my memory if they used the same color wires in those years but should be brown/brown with yellow stripe... disconnect atleast one wire from pack check res between the two brown wires cold...put it back on run till it has issue it pull off atleast one of the wires and check it hot shouldnt be less than about 400 ohms (memory) you may want to look it up... Dave

[mn808gade]

oh ya almost forgot '77s had screw term's ppack, also very high fail rate.H2Operf has you on a good path.-th

[John800]

So is the replacement pack better? Or still prone to fail?
what is the pack you guys are talking about? On the parts diagram i see a stator, timer/pickup, and 4 coils. Am i missing a part or is the timer/pickup an different name for the ppack?

[DanUmbarger]

Seems like this style pack is prone to failure...but then all packs can and will fail for no particular reason...I have replaced many....not nearly as many stators on the OMC's. The powerpack and timer/pulse coils are two different things. The timer base is under the flywheel along with the stator.

So is the replacement pack better? Or still prone to fail?
what is the pack you guys are talking about? On the parts diagram i see a stator, timer/pickup, and 4 coils. Am i missing a part or is the timer/pickup an different name for the ppack?

[flabum1017]

So the replace everything advice came from someone that does not know how to diagnose it? Or did not have the equipment? is there any truth to bad parts wrecking new ones? I fond it really hard to believe.
Would the min max funtion on a fluke meter work? I would think so, or maybe the signal is to fast.

I have seen Stators put out too much voltage and kill powerpacks...... Just check everything and make sure is't all within specs. To find the part that is failing in your case, you will need to run it til it quits then quickly diagnose it before it cools off. I'm going to bet on the power pack. (pulse pack).

[mn808gade]

think this was last yr for single PP.starting '78 omc went to two seperate plug in PPs.USUALLY PPacks fail and will not respark,stators however heatup and fail.is it still sparking?7/16" gap? if yes then check stator cold/hot.PPack is in center rear of motor with all the wires going in-th

[John800]

I really appreciate all the help, i will continue to check this thread so if anyone has anything to add above what has been said go ahead.
I personally have not looked at it yet, but i did get alittle more info on it. Supposedly a shop worked on it a few yyears ago and he never put it in the water. The following spring it acted the same as when he brought it in. They replaced (supposedly) every part that has been mentioned, stator, pickup, ppackand 2 coils. Not sure what went wrong but i am going to try to get a shop manual off ebay and start over.
thank you to everyone so far