1991 Johnson 150 hp hard starting when warm.

[lbbudd2012]

Hello, I've had this engine for about 1 year. Starts up no problem at the docks. After running for awhile it doesn't want to start. It turns over like there's no spark. Once it starts there is a lot of smoke for a few seconds. Then it take about 5-10 minutes before i can give it any throttle. I'll put it in gear and idle away. If I give it gas it will bog down and stall, but will start right back up at an idle. After 5-10 min it runs great. I have read some things about heat soak. This weeked I shut the gas off and let it idle till it stalled. This didn't help at all. It did it twice on Sunday once after sitting 20 min and the other was after 4hrs sitting.

 

[Joe Reeves]

The stator under the flywheel, big (usually green) circular thing, is the beginning of the ignition system and the battery charging system. It contains two large black coils that provide approximately 300 AC volts to the powerpack's capacitor which is needed to energize the pack.

In time those large black coils (one or both) overheat, start to melt down, and start dripping a sticky looking substance down on the timer-base and powerhead. This results in a voltage drop to the pack which in turn results in weak, erratic, and eventually no ignition.

Stators in this condition are known to function (for awhile) when they're cold... BUT... when warm/hot, and cranking at a low rpm, fail completely.

Bottom line... closely visually, inspect that stator. If any dripping as mentioned above exists, regardless of whatever reading you get from it... replace it.

 

[lbbudd2012]

Thanks for the response. I was able to look at the stator today. Attached are a few pictures of it. It does look like it has melted. Is there any way to test/confirm this is the issue? Try ting to avoid spending $250 -$300 just to find out it didn’t fix it. That’s typically my luck. Thanks

 

[Joe Reeves]

There's always a possibility that other problems exist... BUT... what you have shown here in these pictures is the worse melt down of a stator I've seen to date. Regardless of what tests you may think you need to run, I strongly suggest that you don't waste your time. That stator is toast! I'm surprised you were able to start the engine at all.

After you replace is, pay particular close attention that your tachometer operates as it should. I say this as the tachometer operates off of the engine's charging system, a portion of that stator, plus the voltage regulator/rectifier... and if the regulator/rectifier is malfunctioning, the tachometer will be erratic or not function at all. Also, if the regulator/rectifier is malfunctioning (being warned by the tachometer's condition), that allows voltage to back up at the stator which will lead to a not too distant future re-meltdown of the stator plus the fact that the battery will not be charging.

Let us know how you make out, how the tachometer acts, etc.

 

[lbbudd2012]

Glad you mentioned the info about the tach as I was not aware it ran off the stator. I has been giving me erratic readings. Sounds like I should replaced the rectifier also. Thanks for the help!!

 

[Joe Reeves]

Glad you mentioned the info about the tach as I was not aware it ran off the stator. I has been giving me erratic readings. Sounds like I should replace the rectifier also. Thanks for the help!!

Agreed..... I assume your engine has the Water Cooled Regulator/Rectifier (combined) assembly.

Make sure that the battery switch (if so equipped) is turned to OFF while doing the work to avoid accidental expensive shorts, arcing, etc. If not so equipped, disconnect leads from one battery terminal.