Lark racing with LFH's masthead "balloon" jib

Many H-28's were fitted with a 30 hp Universal Atomic Four Gasoline engine in the 60's
and 70's, as were most 30-foot auxiliaries of the era.  They are simple and reliable and could
take quite a bit of punishment.  Here are useful links for maintaining one:
Moyer Marine, Inc., parts and service for Atomic Four engines
Atomic Four manual and parts
More information on parts and service

 H & H  Propeller Company
Autoprop variable self-pitching propeller
Propeller calculator
Another propeller calculator
Use a slip value of 50% for sailboat propellers.

Horsepower: The old rule of 3 hp per ton for an auxiliary suggests 12 hp.  Most people
I know have at least 18 hp in their H-28s, and a few have 11 hp diesels.

Last summer we replaced our Atomic Four with with a Yanmar 9 HP 1 cylinder diesel.
We sacrificed horsepower for light weight, in order to get the weight out of the ends of the
boat to improve performance in head seas under power and sail.  My 31-year-old Atomic
Four was only putting out 12-16 HP (1600 rpm) anyway, and it was all I needed.
The Atomic Four had a 2 1/2 : 1 reduction ratio and a 12" x 6" 2-bladed propeller.

The new 9 hp diesel has proved to be quite sufficient for Lark.  It has a 2.62
reduction gear ratio and a 9" x 14" 2-bladed propeller and a top RPM of 3600.  It pushes
Lark at 6 knots at full speed which is slightly better than the old engine's 5.3.

See also the correspondence between Lark and Yaraandoo about engines.

Yaraandoo's new engine:

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