Bought boat with previous owner saying he used royal purple 10w 40....original owner said he used 20w 50 valvoline racing oil...we use 25w 40 synthetic blend on all our stock mercruisers at my shop....lost a little oil due to loose dip stick.....wondering if I should just top off with royal purple or just change the whole thing....

Depends on how big of a rush your in. Limited time top it with purple royal but when time permits id change over to the 20/50 valvoline. Lots of good old oil threads as well as filters. Someone posted all the different brand filters some time back showing them cut down through the center. Pretty amazing info. You'll find wix being right up near the top.

It has the k&n oil filter....I'm more trying to figure out to stay with a 10w 40 or go to a 20w 50

I mean I'm not racing this boat or beating the snot out of it....it's more of cruising on my lake with the occasional wide open run..... and a few times this summer to big water and ocean...

Id get rid of the kn filter and the purple juice, jmo

Any reason for that and what should I go to? The oil was just done too so I'll prob switch mid summer

I like the 20/50 VR1 you mentioned but dont know what kind of water you run in ( meaning temps ) wix anti drain back 51060R is a good filter choice, but its all preference,

I always have ran brad Penn 20-50 in all my supercharged marine engines.

Same here.

There are a lot of opinions on oil and filters. I Personally like the k&n and mobile one. That's my opinion.