Diesel Engine

The Catalina 34 has had at least three different motors. The M25, a 21hp engine, was installed on the the early models. The M25XP (23 hp) became standard in 1988. The M30, a 4 cylinder producing 28hp, became an optional engine about the same time and is standard in the Mark II. All are produced under the Universal Motors brand (now Westerbeke Corporation). Due to lack of available supplies, the factory occasionally installed a Yanmar engine (note: Yanmars are higher-compression engines, which do not require glow plugs).

Cooling

Exhaust pipe replacement
Heat exchanger maintenance, including zinc change
Heat exchanger upgrade to 3" version to prevent overheating
Hump hose replacement guidance
Overheating as a result of an air lock
Raw water pump: Loss of self-priming capability
Water heater doesn't heat when motoring
Water-lift muffler: Repair or replace?

Electrical

Alternator mount/bracket upgrade Important safety upgrade for M25 (not XP) owners
Engine harness upgrade: A comprehensive overview by Gerry Douglas Important WARNING for M25 owners
Engine harness upgrade by Capt. Al
Glow plug solenoid Installation for faster starting
Secondary start switch
Slow start fix with a wiring upgrade, starter re-build, and new starting battery by Mike Vaccaro

Mechanical

Adjusting Valves: (Be the first to contribute your experience here)
All about alternator belt tension & pulleys
Air Filters (Be the first to contribute your experience here)
Blow by (Be the first to contribute your experience here)
Changing engine mounts
Engine mount protector
Injectors (Be the first to contribute your experience here)
Oil change hose replacement project
Oil pan replacement project to fix leaking oil Pan]
Rebuilding a M25xp by Dave Sanner
Replacement filters, belts, and oils equivalents chart: find alternate replacement brands
Transmissions: changing oil
Transmissions: the right gear while under sail

Misc Projects

Engine Cover Hinge
Outboard Motor Mount

Shaft & Propeller

Flexible coupling installation
Propeller (Be the first to contribute your experience here)
Shaft Alignment
Stuffing box

Also of Interest

Diesel Info at Wikipedia
Engine Manuals
Parts Catalog