Oil weight question?

[ProfitOfDoom]

I changed the oil last fall when I winterized it,and I dont remember what type I put in. I got all my stuff from my local boat store and I told them what engine type I had and they gathered all the stuff I needed, I know it was merc brand just dont remember the weight of it.
I have a 99' mercruiser 454 could anyone tell me what I should be using so I can top it off,Also most shops are closed around here anyone think any harm would come to mixing oil brands as I dont think im going to find mercs brand at any auto place?

 

[Summer Fun II]

I run Mack truck oil 15/40w in mine and the engines don't know differences between oil brands. :smt001

 

[tbirdvet]

Probably 25w40 if Merc. oil.

 

[paulswagelock]

Mercury makes a 25w-40 and a 20w-40 synthetic.
Probably sold you the first one.

You could safely use a 15w40 oil such as Shell Rotella, Chevron Delo or Mobil Delvac for top off - all at Wallymart.
You could also safely use any API rated 30w or 40w straight weight oil. Just make sure it is Sj, SM or SN rated.