What oil for 4.3l volvo?

[Shermanater]

I have an early 90's 4.3l volvo inboard and i'm trying to find out what weight oil to use? I need to change the oil but not sure which to buy. What do you guys use in your boats?

Thanks

 

[Hookin'up]

calls for a straight 30w

 

[combover]

15w40 ams-oil synthetic. the shop uses this for 90% of inboard applications

 

[Shermanater]

Thanks for the help. Don't think i'll put synthetic in this old motor. 30 weight it is.