Started looking a bit more at my motor and can't really understand the design of the exhaust.

The only place the cooling water and the exhausts mix is through a 1/2" hole just before the exhaust hose. (I can't find any other place). There is no other water dump.

What is the small hose in the red circle for?

Pressure equalization in the hump-keeps air pockets from forming.

Ok thanks!

What about the water dump then? I could reach pretty far up on the hump with my arm but couldn't find any dump except the 1/2" just before the exhaust hose.

Shouldn't there be more then just those two (1+1) dumps?!

Not really, ideally you want the water and exhaust to mix as far back as possible to help with reversion. As long as the jacket has water flowing in it the exhaust stays cool on the outside. Then you mix in before the rubber hose to protect the hose. On some dry pipe applications the water just shoots out a tube at the very back and never mixes in the exhaust.

Yes, that part I know. But are those two 1/2" holes enough to dump all the cooling water from the engine?

With your set up you might want to watch water pressure though, different exhaust and crossover setups can cause some pretty strange water pressure-at least put a gauge on it initially to find out where it runs at different RPM levels.

Thanks Ted!