Make: Universal
Models: M25, M25XP, M35A, M35B
Horsepower:
M25: 21 HP @ 3000 RPM
M25XP: 23 HP @ 3200 RPM
M35A: 30 HP @ 3200 RPM
M35B: 35 HP @ 3000 RPM

Kubota Block equivalents

Cooling System: 5 Qts.
Exhaust Hose: MkI: 1-5/8" x 16'
Fuel Filter: Universal 298854 (or similar)
Fuel Pump: NAPA/Facet #610-1051
Injectors: NIPPON DENSO #093500-1560 OR 1570
Oil Capacity: 4 Qts.
Oil Filter: Universal 300209 (or similar)
Water Pump (Raw): Oberdorfer #202M-15, Sherwood #G-908
Depco Pump, online catalog
Marine Parts Source
Water Pump Impeller (Raw): (Oberdorfer) DEPCO #OB 6593, Globe #815, Universal #295628
(Sherwood) DEPCO #9000K, Universal #200175

Here is an EXCELLENT article (by a former C36 owner) on changing a water pump impeller, complete with instructions and photos:
http://www.pbase.com/mainecruising/impeller

Links:
Torrensen Marine, online catalogs
NGK Glow plug cross reference