1998 Johnson 115 wide open throttle stumble

[Triple 67s]

I have a 1998 Johnson ocean runner 115 that starts missing and stumbling at wide-open throttle after 10 or 15 minutes

Still has the oil injection , Carburetors have been rebuilt, fuel tank and lines flushed , New bulb and check valve, pumping the bulb when it starts stumbling does not help

 

[ondarvr]

Frequently that symptom is associated with a coil failing or the power pack. As electronics heat up they may start to fail before dying completely.

 

[boobie]

Sounds like an ignition miss. Put a timing light on each cylinder when it does it, look into the light for black spots. That's the bad cyl/cyl's.

 

[oldboat1]

Is it overheating? Too hot to touch (top of the heads) when acting up, or smells hot? IR gun is always useful.

 

[Triple 67s]

Not overheating I have checked the heads physically right after stumbling and no alarm going off

If I pull back throttle it will run at 4000 rpm for a while before stumbling again

 

[Faztbullet]

Looper or crossflow???

 

[Triple 67s]

Looper

 

[c6mcfall]

Frequently that symptom is associated with a coil failing or the power pack. As electronics heat up they may start to fail before dying completely.

If you got fuel and compression, then agree look at ignition. I had similar problem with mine and it was the power pack.

 

[Triple 67s]

Fuel is good, compression is around 125 on all four cylinders Had several people recommend powerpack and have ordered one

 

[Triple 67s]

I changed out the powerpack this morning and the old one had several cracks in the silicone coating on the back.

Just took it to the lake for about an hour ran like a charm

Thank you all for your input it was very helpful