Tech Wiki

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).


CRITICAL UPGRADES includes a lot of engine information: Critical Upgrades,5078.0.html

RESOURCES – good M25 engine information,from a C36 owner

Spares for a Long Cruise,4590.0.html

Bleeding 101,6377.0.html


The first part pertains more to C30's with M-25s/Oberdorfer pumps, than to M-25XPs -- but it's interesting background anyway....  The second part pertains to all those with Ob pumps, and is subtitled "Yes, you're right ...but we don't tell customers that." --KWKloeber 15 May 2015 
Thanks to Ken for that one, I'm tired of repeating it. - Stu  5/25/2015 


Engine Harness Upgrade from Maine Sail and

Thermostat Sender Source,7985.0.html]]

Engine cockpit panel wiring diagram from, thanks to Noah–z2855-instrument-panel-wiring-diagram.cfm

Exhaust System

The hot exhaust gases are mixed with cooling water in the exhaust elbow and water muffler on their way to the exhaust outlet in the stern of the boat.



[NOTE] The filter interchanges at the above OTT website can’t necessarily be trusted; double-check if you use them.
For instance OTT lists NAPA p/n 3389 for both fuel and lube application. I brought this to OTT’s attention and suggested they correct its list. OTT asked ME to provide THEM all the correct interchange numbers and they would revise the website.
I don’t THINK so.  :-) —KWKloeber 21:33, 29 June 2014 (PDT)

  • note to self. See “manuals” page for Universal Service Bulletins.

Misc Projects

  • Options to Route Crankcase Breather Hose to Air Intake VIEW THE PDF – K KLoeber May 2015

Shaft & Propeller

Also of Interest

Westerbeke/Universal now has the owner manuals online. You can download them at

Kubota Block Equivalents (you have to scroll down)