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Diesel This is a forum dedicated to diesel engines and their applicable accessories.

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Old 02-10-2010
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Universal M25 Series Engine Information

We've been retaining Universal engine information for over twenty years.

Please feel free to peruse our C34 Technical wiki, here: Diesel Engine - C34
Stu Jackson, C34, 1986, M25 engine, Rocna 10 (22#)
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Old 02-10-2010
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We have accrued quite a bit of info on the M25 and the M25XP over at the Ericson owners' site, too, but the Cat 34 guys and gals have theirs better organized.
Good owners' group!

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Old 02-10-2010
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The Universal M5421 and M25 are 3 cylinder diesels based on a Kubota D850 engine block. The 5421 was in production from 1978-1981, and the M25 went from 1981 to 1986. Both engines displace 52 cubic inches, and are rated at 21 horsepower. The M25 was replaced by the M25XP which is based on the Kubota D950 engine block. It displaces 57 cubic inches, and is rated at 23 horsepower.

The M25 was initially released with an alternator bracket that was fastened to the timing case cover. In time, this bracket would eventually crack the timing case cover, and spill oil all over the engine compartment. I have read stories of when the case cracked, it allowed the alternator to fall, and short the (un-fused) positive lead to the engine block. This lead connects directly to the 1-both-2-off switch, and such a failure could result in a fire on the vessel.

This is a picture of an M25 with the old bracket (and a new timing case);

This is a picture of the same engine with a new alternator, and the new bracket;

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USCG Licensed OUPV Captain, ASA 101/103/104/105 Certified Instructor - Also certified in Recreational Marine Electrical Systems

Last edited by eherlihy; 05-16-2013 at 03:22 PM.
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