Another date of Manufacture Question

That's off.

I bought it from a Canadian snowmobile recycler who said they had taken it out of a SkiDoo.  It looks like any other 503 in the Ski DOo repair manuals, same manifold, single Mikuni, CDI bix,

Perhaps the biggest giveaway is the snowmobile clutch assembly that came mounted on it.

I seriously doubt it's ever seen a propeller.

This isn't going well.

UPDATE: Your engine serial 3691623 is NOT in the records for the North American aircraft engine distributor. I checked the paper records again, and I see now that  I originally mis-read  the listing notes.

So it's safe to say that it was instead produced as a Ski-Doo, Sea-Doo, or other non-aircraft variant of the 503 engine type.

But I am pretty sure we can conclude that it was produced early 1987 to about mid-1987, as during serial production it falls between engines 3682922 and 3693155, which are both listed  as received in shipments June/July 87 on the North American distributor's notes (see  pic)

Sorry, this is not an aircraft engine.  The snowmobile clutch on it was a dead giveaway.

Rotax must've been running a duplicate set of books.

A Canadian Snowmobile salvage outfit sold it to me off e-Bay and took it out of a SkiDoo.

Don;t know what to say except i wish I knew when it was made.

Tom Kluberton wrote:

Sorry, this is not an aircraft engine.  The snowmobile clutch on it was a dead giveaway.

Rotax must've been running a duplicate set of books.

A Canadian Snowmobile salvage outfit sold it to me off e-Bay and took it out of a SkiDoo.

Don;t know what to say except i wish I knew when it was made.

 

As I wrote in the post directly above - doublechecking the file corrected my erroneous post earlier - your engine did NOT go through the aircraft distributor, but the numbering indicates it almost certainly was made in early or mid 1987...