cap to upper casing of 90TRLZ fell off, risk?

[dpfundst]

The cap on the upper casing of my 90Hp stroke fell off.
The engine is a 2001 90TRLZ
I have ordered a replacement cap.
I looked into the cavity where the cap was and only saw what looked like access to a bolt for the casing below.

Until I get the replacement cap put in is there a risk with water getting in to do damage? Salt Water

The Yamaha part number is 663-45155-10-00 CAP
It is labled "part 2" Cap in the diagram Boat Parts

Thank u
Dwight

[robert graham]

I believe that square black plastic cap is mostly cosmetic and the motor should be fine without it until your new one comes in. Maybe slap a piece of Duct Tape over the opening for now, just to keep sand and dirt out.

[robert graham]

Also, that cap is access to that zinc trim tab fin bolt down in there. Then when you remove the trim tab, there's another bolt up in there that has to be removed to drop the lower unit...just for future information...

[dpfundst]

Thank you very much!