A precision rebuilt Atomic4 will cost approximately $3500-$4500
depending on peripheral 'upgrades' such as fresh water cooling,
electronic ignition, PCV, external oil filtration, etc. But will
require no new engine beds, no new propshaft and prop, no new fuel
tank, no new engine control panel and no new fuel delivery system.

A diesel replacement will cost in the neighborhood of $11000-$14000 but
requires engine bed. prop/shaft modification, etc. that may further
increase the total cost. A diesel will not increase the value of the
boat when it comes to sale of the boat in future.

Obviously a rebuilt Atomic 4 is a direct replacment. An Atomic-4 is a
very SMOOTH running 4 cylinder engine and doesnt require 'soft' motor
mounts as does a diesel.

A precision rebuilt Atomic-4 (need to 'swap' the old block for new) can
be obtained from www.moyermarine.com. Don Moyer is perceived as the
'worlds 'guru'' of Atomic -4s. You can purchase (with swap) a long
block or short block or a complete engine - depends on your ability to
'turn a wrench'. / mechanical ability.