johnson 79 150 one side cold

[lake11]

I have a johnson 1979 150. I am testing this out of the water with a hose connection. One bank does not seem to be working. I have check the spark at each spark plug and there is spark. One bank seems to be at normal temperature the other is cold. I have taken the carbs off an cleaned them. This is the same side that the control module was replaced early last year, not sure if that is a coinsidence or not. Had problems last year with going from an idle to fast. Also seemed to need a long warm up period. Would falter then get up and go. HELP HELP HELP.

 

[Joe Reeves]

Re: johnson 79 150 one side cold

Install new thermostats that are located in back of the 4 bolt plate attached to the top portion of the cylinder heads.

 

[lake11]

Re: johnson 79 150 one side cold

Would that cause it to not run right. The thing spits and spudders. The plugs on the cold side are somewhat wet. Would the motor run is one side was not working? Last summer I would go to WOT and it would chug and then just take off. Not sure if this is a fuel problem, electrical, commpresion?? What should the compression be?

 

[emdsapmgr]

Re: johnson 79 150 one side cold

You may have a lean sneeze caused by a cold engine. Will normally go away when warmed up. A cold running engine does not promote adequate combustion which can cause poor idling and fuel economy/running problems. Long term, a cold engine can promote carbon around the rings. You may have a thermostat stuck open. You can check the power pack on that side by putting a timing light on each plug wire and read the flashes. Each should be strong, constant. You can see intermittent or weak flashes. I would expect the compression to run around 105-110 on that engine with stock heads.

 

[tashasdaddy]

Re: johnson 79 150 one side cold

do the compression & spark check, while you at it change both thermostats, there cheap insurance. then do a decarb, and get the crap out of the engine. decarb instructions here
http://forums.iboats.com/forumdisplay.php?s=&f=31&page=1&pp=50&sort=lastpost&order=desc&daysprune=-1

 

[lake11]

Re: johnson 79 150 one side cold

I understand the thermostat thing. I am going to do that. Even if the thermostat were stuck open, wouldn't the spark plugs still get hot? I ran it for several minutes. The one side was hot the other still cold.
To test the spark, they talk about 7/16" arch. How do you test that?
How would I know if that bank is getting enough fuel? I sprayed starting fluid in both side and there was no difference in the rpm's, if anything, when I spayed on the side that was running warm the rpm's went down.

 

[brennanpersonal]

Re: johnson 79 150 one side cold

Your power pack has failed. 75.00 for w new on anywhere. Easy to install.
You likely are getting only residual spark.

 

[lake11]

Re: johnson 79 150 one side cold

The power pack on that side was replaced last year. Not sure what brand. If it went bad again, could something have caused it? I am going to switch sides tonight and see if the problem moves.
Again what is a good way to check spark?

 

[Windykid]

Re: johnson 79 150 one side cold

Lake,
Follow Tashasdad,s advice, dont overthink it just do the basic test first then worry about other stuff latter.

 

[lake11]

Re: johnson 79 150 one side cold

How do you check the spark?