2 HP Johnson dies under load

[twocyclemania]

I have an 85 Johnson 2 hp that will not stay running. I just rebuilt the carb (yes it's getting fuel), has spark, and a new plug. It has 90 psi compression (the rings were replaced). It will run high and idle great when the prop is removed; other than that it runs a bit and dies with the prop on it. Also hard to start when the prop is attached. Sometimes it seems like it's firing andstarting to run but it dies (in other words it half as fires). I took the prop off to see if that was enough of burden just before I checked the compression. I have another 2 hp (70's Johnson) with the almost identical compression that runs great. I'm at a loss. The motor in question does not appear to have been used much even though the rings were an issue but were replaced.

 

[Tim Frank]

It may have spark, but is it a viable spark? Jump 1/4" gap with an adjustable spark tester?

 

[oldboat1]

first impulse is to say l.u., but apparently turns freely. Think I would start with the spark too (ignition issue). With an adjustable tester, see what the maximum spark is. Start at a half inch or so (+/-), and drop back if no spark.

 

[Michawilden]

Have you set the pionts to a 0.02 inch gap? And what are the settings for the needles?

 

[twocyclemania]

The coil and condenser are brand new. The spark looks good. I have spark testers but not adjustable. I have a Briggs & Stratton testor with a visible window where you can see the spark jump. The flywheel is off right now so I can't say the exact length of the spark. What I can't understand is why it runs great (high speed and idle) with the prop off but the extra load of the prop seems to be enough to put the motor over the edge and not run. The points have not been replaced but I don't see them as the problem since it does run great when not under load (points set). As for the needle settings they were both adjusted (with the prop off) to the best running; both idle and high speed. The numbers on the dials mean nothing- just a point of reference. Another mystery motor. I've found some run great and others seem to have a 'ghost.' This is one of them. Hope somebody can solve this as it's really a simple motor. Just a thought; could the ignition wire be the problem? I've replaced everything else.

 

[racerone]

You can not properly adjust the carburetor with the prop off the motor.

 

[Vic.S]

The coil and condenser are brand new. The spark looks good. I have spark testers but not adjustable. I have a Briggs & Stratton testor with a visible window where you can see the spark jump. The flywheel is off right now so I can't say the exact length of the spark. What I can't understand is why it runs great (high speed and idle) with the prop off but the extra load of the prop seems to be enough to put the motor over the edge and not run. The points have not been replaced but I don't see them as the problem since it does run great when not under load (points set). As for the needle settings they were both adjusted (with the prop off) to the best running; both idle and high speed. The numbers on the dials mean nothing- just a point of reference. Another mystery motor. I've found some run great and others seem to have a 'ghost.' This is one of them. Hope somebody can solve this as it's really a simple motor. Just a thought; could the ignition wire be the problem? I've replaced everything else.

Check, clean, and reset the points then. Clean means CLEAN!

Is the coil correctly positioned on the armature plate

SEE http://forums.iboats.com/forum/engin...s-on-old-omc-s

Check the spark . Inspect the HT plug wire. If you do it in the dark you should see any insulation failure.

Is the plug correctly gapped to 0.030"

Make sure you have tightened the packing retaining nuts on the carb needles so that air cannot be drawn in, (#16)

is the carb float correctly fitted and is the height correctly set. Is the little spring clip between the needle and the float arm fitted (#20)

Check that at full throttle the throttle pate in the carb is fully open.

Check that you have good fuel flow to the carb
Gently seat the carb needles and then adjust them to the basic settings.

Fit the prop and finely adjust the slow running needle in the test tank

Then fit the engine to the boat and take it out on the water to finely adjust the high speed needle

SEE http://forums.iboats.com/forum/engin...-by-joe-reeves

BTW fuel mix ix 50:1 even if the decals or the owners manual says different!

 

[oldboat1]

Maybe a tank/cap venting issue, maybe partial tank valve blockage.

 

[twocyclemania]

Thanks for all the suggestions. Frank, I did your check list. I went back in and went over the ignition. Believe me, the points are cleaned and set. The plug is set. I disconnected and cleaned the mag plate ground wire. I removed and replaced the welsh plug on the carburetor; something I didn't do when I rebuilt the carb. It was spotless inside the chamber and the three small holes were open (put a wire in them). The spark in the visible window of my spark tester is crisp and better than 1/4 inch and it's consistent. I checked again and it's getting fuel. Ran it in the barrel today and it ran decently at high speed and mid range. I attempted to give it another rough (not out on the boat) adjustment but than it just died. Once again, it's hard to restart. When you pull it it seems like the motor is 'assisting' you and it's getting ready to take off but it doesn't I'm going to check tonight in the dark and see if there are any visible spark problems like the ignition wire but other than that I'm at a loss. As for the cap/venting. I took the cap off, but other than that there's plenty of fuel flowing when I disconnected the gas line at the carb. Such a simple motor I can't believe it's such a ???

 

[oldboat1]

fresh gas, 50:1 mix (not leaner).

 

[frustratedboater]

Might be a silly question, but are the reeds in the right way, or seated correctly? I just had my 57', 7.5 Evinrude, have a piece of dried gasket sealer stuck in one of my reeds and had similar symptoms... Just checking.

 

[twocyclemania]

Almost everyone contributing on this site has had problems and/or solutions and everyone is especially entitled and encouraged to provide a follow-up; especially when it may help someone else. So here it is. I finally solved the problem with this motor. I'm not sure if it was created by me or the previous owner since my memory of what I've done most often fails me; especially when you're bouncing between motors. I really should keep a written log. The reason the motor would not handle the 'extra' burden of the prop was due to the impeller housing cup being upside down. Not only did this 'bind' the shaft/impeller but coolant was very restricted. Almost non-existent. In other words; the motor was burdened to the point where it was difficult to start but it would soon overheat. This is why it would not re-start after a short while. I hope this info helps others and I hope I was not the 'idiot' who did it. Some of you folks who responded are experts and I hope you remember this. It's amazing what can go wrong and what idiots can do. Thanks for all your advice and help. By the way the motor starts right up, cools perfectly (with the prop on), idles and has high end. I'd trust her out on the water. Thanks!

 

[Tim Frank]

Wish there were more posters with your attitude....
Best of the season and thanks for closing the loop.

 

[oldboat1]

Yup. Thanks for coming back -- and already part of the literature! (http://forums.iboats.com/forum/engi...-outboards/10096684-81-johnson-2-hp-won-t-run)