Joe is talking about the old "A.I.R." pumps (Air injection reaction). It was some crazy thing that an engineer thought up, in the 70's. The idea was, if you inject fresh air into the exhaust... it would help run off any leftover hydrocarbons. In reality... all it did is add complexity, and dilute the exhaust (for an emission test)
As far as a Di system in the automotive world... it's just now starting to catch on. (15 years after the boat and PWC world discovered it) Nissan is using it on a lot of their engines.
Anyway... as Joe said... it's not running without it.
There shouldn't be a trick to uploading pics. But, I personally find it easier to just load them on a site like "PhotoBucket", and then use the "IMG" tag to link them back.
On the air pump, the entire crank unit will come out. There should be 4 bolts around the flange... and you can wiggle it out as a unit. Once it's out... you can see if there is any damage inside.
The crank is sold as a unit... but I think there is a snap ring, that will hold the hub onto a tapered shaft, with a key. Unfortunately... since it is sold as a unit... I can't tell. But, in my years of playing with outboards, I can't say I've heard of the crank assembly going bad. Normally, the valve system gives out, and you lose pressure, or the pump simply wears out.
