Originally Posted by eherlihy
...also Beta marine makes a 28HP A4 replacement...
Did some searching and Beta also makes a 20 hp replacement for the A4. Did Atomic make a 20 hp motor? In any case, it seems that "replacement" means that it fits on the A4 mounts. So, height/length could still be an issue.
A Beta dealership site states:
Several Beta Marine diesel engines are available to replace the Atomic 4 gasoline engine depending upon the vessel's displacement. General guidelines for displacement hulls follow, but please contact Joe DeMers for a specific recommendation concerning your boat and application.
Boats between 10,000 and 14,000 pounds need the Beta 20 or Beta 25 engine.
Boats between 14,000 and 18,000 pounds require the 28 hp Beta Marine engine.
The Alberg does have a narrow beam (9'-8") by modern standards, but also has less LWL (24') and a full keel. At 12,600 pounds, that would seem to put it at the top of the first category (Beta 25), or bottom of the second.
Another thread I was looking at, pointed out that charging takes additional hp, something I didn't even consider.