Kawasaki Stand Up Jet Ski

it looks like a plug resivour oil, but did not mark and I do not see oil in the compartment. it is removable by hand and I want to know its purpose. In addition, the ski has not been executed for a year, but has so early. I checked all the obvious things like pieces of rubber (for cracking) has tightened the clamps, etc. Is there anything else I should look?
Thank you!

Please do not put oil in there. This is indeed the sheet where you check the timing of the engine. Usually never need, but after some engine repairs if you need to check you delete that file and the strobe light use. I have a 89 650 SX that I bought new, so everything about this card. :-) If you were in the discharge of oil there, you ruin the Assembly truck behind the wheel and your ignition unit also ensure that the button to fire up that looks like a starter on an engine Regular is still closed, because it is the drain valve drain at the bottom of the engine should have water in it in diving it in waves. Most people who used to race these blocked the whole assembly off a plate on the bottom of the engine, as if this is left open a bit the engine runs too lean and burned pistons. I always check to make sure mine is all down before getting one day. I suppose the years 550 have what my 650 does, but if yours does then just disregard. :-)