62 40 hp Problems "Help"

[tinker2584]

Thanks to CAtransplant for identifiying my engine.1962 Evinrude Lark IV;hot water acuated choke,non ajustable high speed on the carb.<br />Here's my problem:<br />It starts ok and idles but misfires at all speeds(runs smooth then a bang and motor shakes in its mounts for a split second then runs smooth again for a few seconds). It lacks power at wide open. Throtle linkage is ok, butterfly opens all the way.Fuel in the glass bowl stays at mid level, but when I pump the bulb engine rpm stay the same.If I close the choke at wide open it runs the same ,then slows down afterabout 3 seconds. Spark plugs are last years. Upper cylinder orange spark, lower blue.Can these motors run on one cylinder?Could unburned fuel be burning in the exaust? I forgot to mention, when it misfires,a burst of blue exaust gas comes out of the upper water-exaust port.<br />Great forum guys!! I also have a 58 Johnson 15hp and a 56 Evinrude 35hp that I would love to bring back to life.<br />Any help is appreciated.<br />Thanks

 

[DCT]

Re: 62 40 hp Problems "Help"

Sounds like you have a misfire on one cylinder. By the way you explained the color of the spark, blue on lower, orange on upper, you should remove the flywheel and check points, coil and condenser. Both cylinders should produce a nice blue spark if everything is in proper condition.

 

[Blueclaw]

Re: 62 40 hp Problems "Help"

time for a tune up. points, plugs, condensors.

 

[CATransplant]

Re: 62 40 hp Problems "Help"

Yup, I think it's going to be time to pull the flywheel on this one and check the coils, points and condensers. You may also find a partially sheared woodruff key that is part of the reason for your backfiring or sneezing. I'm not certain, but that could be it.<br /><br />All the parts are available through any NAPA auto parts dealer, and they're not horribly expensive.<br /><br />Check the following thread out for good info:<br /><br /> http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=28;t=029310#000017 <br /><br />You'll also want your manual on hand for this job. I wouldn't do it without one.

 

[CATransplant]

Re: 62 40 hp Problems "Help"

Another thing that can cause the problem is points that have a too small or too large a gap. That changes the timing of the spark, and can cause backfires, as well. You'll still have to have the flywheel off, though, unless your flywheel is one of those that has an inspection port, which will let you check point gap and adjust.