1977 Johnson 35hp running rough

[Alex Ernst]

My 1977 Johnson 35hp is running very rough at idle. I am new to working on outboards, and have learned much this summer. I rebuilt my carb, changed the plugs, adjusted idle speed and did a link and sync. The engine is still idling rough, and yesterday started running on one cylinder at idle. It seems to start running on both when I get to a higher speed. The compression is good in both cylinders. I can pull the top plug wire at idle and nothing changes, she just keeps running. I did a spark gap test and it will not reach to 7/16 " as I have read it should. I'm not sure what my next step should be, and any help would be greatly appreciated.

 

[fireman57]

If you can pull a plug wire and nothing happens you are not getting spark to that cylinder. Sounds like a bad coil. Physically swap the coils not just the wires and see if the problem follows. If it does just replace your coil.

 

[Alex Ernst]

I changed the ignition coil on that cylinder, with no change in performance.

 

[Alex Ernst]

I also changed the rectifier because it tested bad. The starter motor is cranking well over 250 rpm, the recommended speed. I guess I have to do some more troubleshooting.

 

[fireman57]

If you have weak spark, and you say it won't jump 7/16' and bright blue, then you will run on one cylinder. If you are sure when you changed the coil that you got the wire in all the way then I would lean toward your cdi getting weak or bad. If you have one of the old style coils where you have to assemble it yourself it is hard to get the wire seated in the coil all the way. Also, make sure you coil grounds are clean and that wire isn't bare or cracked.

 

[oldboat1]

Did you swap coils between cylinders, as mentioned, or did you change one out for a new one? Also, were you adjusting the idle stop (throttle), or the carb needle? Finally, on that spark gap test -- using an adjustable tester set at about half an inch?

If you put in a new coil, chances are you had to assemble it -- some tricks with that. If you were adjusting the carb idle mix, some tricks with that. And if checking spark -- well, not much of a trick there (just want to be sure you are talking about a tester setting).

 

[Alex Ernst]

I did not swap coils, but just replaced with a new one. I was very thorough about making all the connections properly. I have adjusted the idle stop, and the carb needle. The idle stop I set to where it seemed to idle without stalling, and the carb needle the recommended 1 1/4 turn back from the seated position. I did check the spark with an adjustable tester, set at 7/16". I am waiting for a new power pack in the mail, and hope that does the trick. I have also begun to gather tools for removing the flywheel to look at the magneto.

 

[oldboat1]

1 1/4 would be an initial mix adjustment (carb) to get the motor running -- permits final adjustment. With the engine warmed up and in gear, would lean it out clockwise about 1/8 turn at a time, letting the motor catch up between adjustments. Would expect rpms to increase with a leaner setting (reduce rpms with the throttle setting or throttle idle stop). If it lean sneezes or stalls, back it out about 1/4 turn. That should be pretty close to the setting you want.

Spring connector spikes at the plug and coil need to be driven through the wire in contact with the core. After assembly, doesn't hurt to test continuity between connectors just to be sure.

(ed. carb settings on the boat, btw -- best -- or in a barrel. On muffs won't quite do. Need back pressure.)

 

[jimmbo]

The 35 was never a really smooth idling engine, at least ours weren't.

This link should take you to some info http://www.boatinfo.no/lib/evinrude/manuals/1971-1989johnsonevinrude.html#/212 page 213 or section 5 page 51

 

[fireman57]

jimmbo it's funny you say that but my brother's '76 is rough idling also. It doesn't die just sounds bad.

 

[Alex Ernst]

Thanks for all the advice. I replaced the power pack today, with no change in operation. How do I test my new coil for continuity between connectors? Do I just hook up my meter to each end and see if current flows through?

 

[Alex Ernst]

I have pulled the flywheel and am looking a everything underneath. I drove a short distance today, and it still seems that the 2nd cylinder is kicking in at higher rpm's, and the engine has full power.

 

[oldboat1]

This is a good discussion of coil testing: http://www.penn.itgo.com/video-pages/coil-testing.html I was referring to simply measuring continuity when new wires are assembled (measure between boots, if that type of assembly). The spring-clip-to-wire connection can be an overlooked issue that will prevent spark.