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1973 18hp evinrude starting issues

B

bugginout

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Was running the motor when it backfired hard, which caused it to shear the key and cracking the points collar. I have replaced both of those. I've also replaced the points, condenser, and driver coil. It has good compression, set points at .020 on where it says top. It gets spark, but will not start. Any help will be greatly appreciated, Jerry
 
Sorry for taking so long the bottom will jump the 5/16 but not the top changed coils and it jumped the gap going to replace coil and try again
 
Did you use a factory key, yes or no.---------------Torqued the flywheel nut ?---------------If still hard to start look at the detent on the choke lever.----A wee plastic piece and is known to break after many years.
 
Somebody in the past probably used an impact wrench to tighten the nut. That spread the taper in the flywheel, causing it to fit lower on the shaft, which in turn let it squash against the cam, breaking the cam. Flywheel is ruined. After you get a good one on there, proceed with troubleshooting the ignition. And use a torque wrench and make sure the tapers are clean and dry.
 
With the external coils .022 is closer to correct but the best way to adjust the points is with a timing light. On the side of the magneto plate is two marks shine the timing light at those two marks and the single mark on the flywheel needs to be inbetween the two marks. It can be time consuming but the engine will purr like a kitten once you get it timed properly. Any 12 volt battery will work and clip the reluctor on the plug wires and check it either running or while cranking. There are two marks on the flywheel 180 degrees out one for each cylinder.
 
Check your service manual for the proper carburetor synchronization setting of the cam follower. My book only goes up to '70 so I'm not able look it up. Some year models are set differently relative to the mark on the cam. My '65 Johnson is to be set dead on to the mark, some are to be set just before or after the mark on the cam. Make certain this setting is as close as you possibly can make it to what it calls for. I just went through this with my 18. I did a complete tune up replacing all ignition and fuel components and was surprised when all I would get was a mild backfire. I rechecked my point settings but got the same results. "Timing" seemed to be my issue (ie the backfire) so I began to read about "synchronization" and it's importance. I made some adjustment to the cam roller/follower and away it went ! Made some carb setting refinements and it's running great, starts right up.

I now have three of the older model OMC engines and I've invested in a timing fixture to set the points. Used in combination with an Ohm meter I can set the points as precisely as one can with no guess work. There are several You Tube videos you can watch to explain the procedure and give you a line on where to get your own timing fixture. Here's the link: Good Luck ! https://www.youtube.com/watch?v=eNK2TEeQQv0
 
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You could have blew the crank seals out put some fuel mix directly in the plug holes and the see if she pops. I just use a length of vacuum tubing dunk it into the fuel tank and plug the end with your finger then stick it in a plug hole and release your finger.
 
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