Hello everyone I'm new here and to mercruiser. I bought a 1987 four wins 245 vista with a 5.7 mercruiser can anyone tell me if it is in the outdrive or the motor. Or is there one in each. Thanks
This sort of depends on the stern drive model you have which being a 1987 technically should be an Alpha stern drive so normally the impeller will be located in the drive mounted to the lower unit gear case housing.
Now if you happen to have a Bravo drive or sometimes if you have a closed cooling system (Antifreeze) then there could be a chance that you have a sea water pump mounted to the engine typically found on the lower left-hand side when facing a stern drive engine model.
If I might suggest, as a new boat owner you should seriously consider getting a Mercruiser service manual for your engine/outdrive. You will find it to be money "very" well spent and will be able to answer many if not all your questions.