Type of oil for 3.0 mercruiser

[Tuckin22s33]

I bought my boat 3 months ago it's a 91 stingray with a 3.0 mercruiser LX. I have had to do some work to it before it was ready to use finally get to the point of using it this weekend. After running it all weekend I have noticed it has an oil leak which I am going to address. I ask the guy I bought the boat from if he used conventional or full synthetic he said he could not remember but he said it was a strange weight to him it was a 0w20 which I have used in a Chevy truck I had that was full synthetic. So my question is does that weight sound right to use in motor or should I go back to a different weight and also do I stay with full synthetic now just incase that is what he run in it. Any help will be greatly appreciated thanks

 

[Scott Danforth]

welcome aboard

no, your 3.0 uses 20W50, straight SAE 30 or SAE 40 or my preference, Rotella 15W40 diesel because it has zinc you need for flat tappet cams

0w20 works well in a brand new roller motor, however would not work in your 1950's designed 3.0

 

[Scott Danforth]

also, if the oil leak is from the front of the motor, is most likely is the timing cover rusted thru. that requires the motor to be pulled

 

[Tuckin22s33]

Scott Danforth thank you that's kind of what I was thinking too just wanted a second opinion and yeah run rotella in most my stuff I have so the boat will fit right in. Haha on the oil leak i am taking it that is a common problem on them that is right where it is leaking from. Pulling the engine is no problem already did it once just rebuilt the transom in the boat. Thank you for the help I have got a lot of good info from this site and you guys on here just decided i would join and ask stuff for myself. Thanks again Scott.