The "stroker" that you're talking about... I'm not sure if you know this, or not, but Merc produced a 383/6.2L motor that was a regular, off the shelf engine. Could this be what the owner of that 240SD had installed? It uses regular gas and the difference in fuel economy vs the 5.0L MPI is only one or two GPH at cruising speeds. However, that difference often comes even closer together since the 5.0L has to work harder to do the same job.I ended up passing on the boat with the stroker motor and buying one with a stock 5.0 motor. It sounded like it would have been nice to have the bigger motor, but I didn't want to spend twice the amount of money on fuel every time we took it out.
That, which has NEVER been said in the history of boating... "I should have gotten the smaller engine"