1985 johnson150 hp j150txcos idle trouble

[liorlilah]

Hello everyone.
i have an engine for about 2 month we replace all the fuel line and rebuild the carbs as the boat had set for 3 years.
when we start the engine it runs good at around 1100rpm but after a minute it will sometime jump by itself to 2500-3000 rpm. does anyone have any ideas on what can make the rpm jump like that.
thank you.

 

[liorlilah]

Re: 1985 johnson150 hp j150txcos idle trouble

Any ideas?
Please.

 

[emdsapmgr]

Re: 1985 johnson150 hp j150txcos idle trouble

Check the spark on each plugwire. All the plugs may not be firing. It's possible that the engine is only running on 3, 4 or 5 cyls at 1100 rpms. When all 6 cylinders kick in, it will go up to 2500. You can do a cyl drop test, or check each with an inductive timing light.

 

[monnewbie3]

Re: 1985 johnson150 hp j150txcos idle trouble

Are you running 1100 Rpm on muffs or in water? Does the engine smoke and sputter?
I would check your timing to start and see what happens

 

[liorlilah]

Re: 1985 johnson150 hp j150txcos idle trouble

thank you, i will check mi timing today and let you know, i am running the engine on muffs. the engine does sputter just at the exact moment when it start to go up in rpm.
thank you monnewbie3 and emdsapmgr.

 

[liorlilah]

Re: 1985 johnson150 hp j150txcos idle trouble

Ok. i check the spark on the all the cylenders and on starbord ther is no spark on all 3.
what should i check i switch the power packs around and it did not change anything.
could it come from the timer base? or stator,regulator.
let me know what you hing
Thanks you

 

[emdsapmgr]

Re: 1985 johnson150 hp j150txcos idle trouble

The power pack swap is a good test. Two other potential sources of problem: the stator or the timer base. The factory service manual tells you how to qualify them. You may find also relevant troubleshooting information at this website: cdielectronics.com