Diesel Engine

The [Catalina 34] has had at least three different motors. The M25 a 21hp install on the original 1986 boat, the M25XP and the M30 a 4 cylinder installed on the Mark II

Cooling

Raw Water Pump

Engine Thermostat

Replacing Engine Zinc

Mechanical

Injectors

Air Filters

Blow by

Oil, Filters and Changing oil

Drive Train

Flexible Coupling

Shaft Alignment

Dripless Packing

Goretex Packing

Adjusting Packing

Electrical

Engine Harness Upgrade

Adjusting Belt

Alternator

Glow Plug Solenoid

Also of Interest

Diesel Info at Wikipedia