The 27 was offered in both outboard and inboard options. I think at first most were delivered as outboards, some were ordered with the optional inboard (Vire 7 hp at first, later Universal Atomic-4, both gas. Diesel might have been available for 1978, the last model year). I suspect many of those outboard powered 27s have since been updated with inboards, most probably with Diesel inboards, although a few were upgraded from outboard to the OMC Zephyr 2-stroke sail-drive.
As far as I know, ALL of the 28s came from the factory with inboards, original standard engine was the OMC Zephyr (15 hp), later the optional Diesel became standard (various engines and horsepower offered over the production run). Some owners have changed to outboard power on the 28, I suspect many of those were originally powered by the OMC Zephyr and when it wore out it was easier to glass over the hole in hte bottom and botl on an outboard bracket. Some of the OMC equipped boats were updated by owners with a Diesel inboard (sail-drive or shaft and strut).
Do you have a pic of the "mystery" boat? The 27 had two interior versions based on model year, early models 1973-75? had the galley along the starboard side of hte cabin with a settee along the port side. Later the galley was moved to the aft end of hte cabin in hte aft, starboard corner.
I'm not sure what would make a 28 look like a 27...... but if the 28 had the optional opening ports replacing all the typical fixed ports..... it could be confusing since those 28s (few were built that way) sure look "funny" compared to a typical 28... I once saw a 30 equipped hte same way, almost did not recognise it as an O'DAY 30.
Original (1979) cabin layout on the 28 was nearly a mirror-image of the 1977-78 models of the 27. Table appears bigger on the 28 and the galley was in the Port-side, aft corner.
