August 12, 1960
Bulletin No. SB-797
Trouble shooting
SUBJECT: PROPELLER PITCH 40 & 75 H.P. ENGINES.
One of the most important parts of an outboard motor is its propeller. This rather
simple part has a big job to do in converting the energy produced by the powerhead
to usable power in the form of thrust necessary to propel the boat. Bearing this in
mind, it is easy to understand why the balance of the propeller is as important as
the balance of the crankshaft, rods, and pistons in achieving top performance.
Propeller balance may easily be upset by a blade that is not pitched properly; that
is, one that has been knocked out of pitch in relation with the others due to
striking an under water object or similar accident. This blade will then do either
more or less work than its neighbors, depending upon which way it is bent, resulting
in unequal forces being transmitted to the propeller hub. These forces are then
directed through the whole motor and are evidenced by varying degrees of vibration
and rough performance. Some of the more extreme cases may actually cause structural
damage to other parts, although the usual results are loose screws and parts falling
off the engine.
Be sure your service department is well equipped with the latest propeller straight-
ening fixtures as the importance of a correctly pitched propeller cannot be over
emphasized if top performance is to be expected.
The following propeller fixtures are priced as indicated below. All orders should
be placed through:
OUTBOARD MARINE CORPORATION PARTS DEPOT
GALESBURG, ILLINOIS
75 H.P. 10-1/4 x 10 Part No. 378122 $12.00 ea. net
10 x 11 Part No. 378135 12.00 ea. net
10 x 12 Part No. 378134 12.00 ea. net
40 H.P. 10 3/8 x 14 Part No. 378136 12.00 ea. net
10 3/8 x 13 1/4 Part No. 376951 12.00 ea. net
10 3/8 x 12 1/2 Part No. 376106 12.25 ea. net
10 3/8 x 11 1/2 Part No. 377539 12.00 ea. net
JOHNSON MOTORS
W. W. DeWees
W. W. DeWees
Service Department
WWD:eb
NOTE: Post on your RD and V4 index - 40 & 75 H.P.