The Universal Atomic 4 is a gasoline engine that, though out of production for many years, still powers a large percentage of sailboats.
[http://www.alberg30.org/atomic4/ Care & Feeding of the Atomic 4]
[http://www.geocities.com/atomfour/ Captain Ron's Atomic 4 page] includes a copy of the little owner's manual that came with the engine.
[http://www3.bc.sympatico.ca/Atomic_4_Eng_Service/History_of_the_Universal_Motor_Company_1.html Robert Hess' history of the Atomic 4] Hint, it's not a jeep or tractor engine.
[http://home.earthlink.net/~freighter/engine.htm Chris Wilson's photos of an Atomic 4]
[http://www.classicsailboat.com/atomic_4_comments_and_tips.htm Joe Palmer has some tips]
Theodore Enders describes adding a [http://homepage.mac.com/tenders/atomic4.htm High Temperature Alarm]
Sea Magazine has an [http://www.seamag.com/sea_web/march01/hob.asp article describing a tune-up] online
A parts catalogue showing most of the atomic four engine parts and description of them is available in PDF format at [http://www.pearsonvanguard.org]
The Atomic 4 owners manual and repair and maintenance manual, in PDF format [ftp://ftp.sailnet.com/tartan/Atomic4/Manuals/]
Sailnet hosts an [http://members.sailnet.com/email_lists/processing/index.cfm?list=atomic4 Atomic 4 mailing list]. I recommend joining and asking your questions there. You can also search the [http://archives.sailnet.com/arsearch/atomic4/threads.php message archives] of that list.
A catchall page for EngineRelatedInformation.