Age and info

3561689 was produced 02-July-1985

Unfortunately, that  is so ancient that there is zero additional information in the current factory database (not even a confirmation of model number / engine type!).

I assume you have already read the 'modern' 503 manuals (found at https://www.rotax-owner.com/en/support-topmenu/engine-manuals#447-and-503-engines)

Maybe have a look at the older historical version found here: https://www.rotax-owner.com/en/support-topmenu/engine-manuals#2-stroke-historical-documents

Do you have the engine logbook? Can you post some photos of your engine here? 

Thanks for the info. At least I know now when it was build. It’s in an Ultralight I just bought at a good price. Want to put a electric starter on it and not sure if the kit that Aircraft Spruce sells will adapt to this engine. The serial number that i gave you is 356-1689. I’ve ask Aircraft Spruce about it fitting but they haven’t really replied with correct answer. I think theyre not sure. I know this engine came with a recoil starter, just wonder if it ever came with electric or would the new ones AS sells fit. They’re numbers are not 15-05370. Says its supposed to fifty all the small rotax’s. The reason I sent you original e-mail was to find out the year so I can track down a starter. As far as a manual the ones online will do. I’m familiar with this engines from having Skidoo’s long ago. I’ll try and send some engine pics here also. It is a 503, single carb.