I have a couple of those and they’re a fun little motor. Garry Spencer, AOMCI Member whose dad worked for Evinrude the 30s & 40s (I believe), says that this little one-lunger is the best motor they ever made (Evinrude, Johnson and Gale (makers of their own brand motors and those badged with store names like yours) were all one company at this time).

I don’t know of a rebuild ‘manual’, but I started with Cheap Outboards by Max Wawrzyniak. He takes you through all of the things to check to determine whether or not your motor is a ‘good’ candidate for restoration. I have a parts manual for this particular motor that I will try to post should I find it.

As for parts, you can still get some replacements. As I recall, this motor has what is known as the ‘horseshoe’ ignition coil. I have never seen a replacement one of these, so yes, you will need a parts motor if your coil is bad. Condenser, points, spark wire & boot, and spark plug are available new from different suppliers (I believe). You’ll need some kind of puller to get the flywheel off. I used a cheap one from HarborFreight before upgrading to a real OMC (name of combined Evinrude, Johnson, Gale company) earlier this year.

You should be able to find a carb kit here: http://discount-marine-parts.com/. I have purchased stuff from them before and been satisfied.

You’ll want to check the water pump impeller which on those motors, again as I recall, rotate on the prop shaft. If you need a new one of these, you might be able to get it here: http://home.earthlink.net/~flyingscott/index.html

Now, as to your particular problem, it could be something binding up under the flywheel or it could be a broken/misshapen piston ring or it could be something wrong with the gears/pinions between the driveshaft and the prop shaft — these problems range from not hard to fix to devastating. When you get the flywheel off, have a look at the crankshaft and associated flywheel key for any signs of violence over the years. BEFORE DOING ANY OF THE ABOVE IN THIS PARAGRAPH, however, you may be really lucky and the motor is only suffering from not having been lubed in several decades. Take out the screws in the lower unit (one vent, one fill) and see what, if any, grease is in there. It could be all it needs is new grease (Lubriplate 10 https://www.napaonline.com/napa/en/p/BK_7652651/BK_7652651 or John Deere Cornhead grease. Also, squirt some two-stroke motor oil into the cylinder and rotate the flywheel by hand to see if that loosens it up. In order, I would check the lubrication first (cylinder and lower unit), under the flywheel second and the engine third.

This ought to get you started. Good luck!