Bill, if you look at the 2001 380DA Owner's Manual and Parts Manual, you'll see that this boat came with log mufflers. That would make those waterlifts replacements. It could be that someone already blew something and had to have an engine rebuilt, which opened that owner's eyes and caused the change to the muffler system. Heck, for all you know these are replacement motors. I don't know if there's much difference btwn the HO and the regulars, but all Gen VI 7.4s had sea-water sucking tendencies. 260 hours is plenty of time for the problem to happen, and if the motors are original, that low usage pattern has left a LOT of sitting around time for any water to lay on the innards and cause rust and corrosion. I was the 4th owner of my boat. I don't know who replaced the engines - I only know when the were replaced. Can you get any info from the broker or previous owner? If you jot down the serial numbers of the engines you can see if they're sort of close numerically and you can call Merc and get the actual date of manufacture.