For all you older P-323 owners (the boat, not the owner!):
My 1977 P323 came with the original Atomic-4 engine. After 33 years of raw-water-cooled service in the Chesapeake Bay, it gave up the ghost in 2010 with a cracked block,
due to improper winterizing by a previous owner.
Faced with a repower, I did a lot of research. Despite much pressure from many sources to convert to diesel, I concluded that it did not make economic sense for many reasons.
The P323 is a poor candidate for gas to diesel conversion due to it's V drive. It won't fit any current production diesel, and must be replaced as well, further upping the cost.
In addition, current diesel V drives have a different V angle than the original Walter V drive, necessitating extensive surgery on the engine mounts.
I found that there is nothing wrong with an Atomic-4 powerplant. There is a STRONG user base support. 40,000 were built, and aprox. 20,000 are still in service. Parts,
castings, and whole rebuilt engines are still available. Its a simple, easy to understand and repair engine, which means a lot when you're out cruising.
Not to mention $4 spark pulgs vs $1000 injectors!

In addition, Moyer Marine, the premiere A4 support source, recently announced that they are now producing newly cast A4 blocks!
The purported 'risks" of a gas engine vs a diesel turned out to be mostly fluff. True, diesel wont explode, but virtually all diesel owners still carry gas onboard to power their
dinghy outboard. And many of them think nothing of using propane, which carries the same risk of explosion as gas. The bottom line is that you
always have to observe
proper precautions and maintenance to avoid a fire or explosion, regardless of your powerplant.
In order to balance between time and money, I elected to tear down my old engine to a "short block", and replace it with a professionally rebuilt short block from Moyer Marine,
reusing the major external components (alternator, head, manifold, carb) off of my old engine, as they were all less than 5 years old.
It was absolutely necessary to cut out the cabinet strut to get out the old A4 and replace it. I came up with a clever way to minimize the visible cut lines when it is reassembled.
My rebuilt A4 runs great. Smooth and quiet, due to it's 4 cylinders, unlike the 2-cylinder MD11C.
Adjustable engine mounts made alignment very straightforward, and I highly recommend them.
My total cost was between $5k - $6k, including converting to fresh water cooling.