Re: looking at boat with 1991 5.7 l cobra 350...
Maintained as they should be I don't think the Cobra is a bad unit. Problem is OMC has been gone for quite some time. Finding parts is not always easy, they can be had but they are usually not at the local marina. Finding someone who knows how to properly work on one if you're not the mechanical type can be challenging. Could be a lot of things, bad rings, bad valves, and yes, bad head gasket. But even the good cylinders are low. Good news is GM engines are easy to come by and even a rebuilt marine version from someplace like Rapido wont break the bank. My last boat had a Cobra drive, and while the drive didn't give me any issues I wouldn't buy another simply for the reasons listed.