Dave Gerr - Boat Mechanical Systems Handbook-How to Design, Install, and Recognize Proper Systems in Boats

surprising how often I’ve learned of boats

that had humplike protrusions molded into

their bottoms as an afterthought to fit the

proper gear. This is always bad and always

wrong, and there’s really no excuse for it if

the design is done properly to begin with.

I can usually find the gear configuration I

want. Sometimes, however, even an exhaus-

tive search shows that what I’m looking for

just isn’t available at the rpm, power, and

torque ratings needed. If this happens, you

have no choice but to go back to the drawing

board. The most common instance of this

occurs when you are looking for any form of

gear with reduction ratios deeper than 3:1 on

engines under 300 hp (224 kW). Such gears

don’t seem to be made. This is a shame—

particularly on displacement-speed vessels—

as larger reduction gears would allow larger

and more efficient propellers. The resulting

improvement in fuel economy (as well as low-

speed oomph) would be highly beneficial.

PART ONE: DRIVETRAIN INSTALLATIONS

Figure 3-1.

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