Boat And Engine Performance; Boat Bottom - Mercury MerCruiser MCM 454 Mag MPI Service Manual

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SERVICE MANUAL NUMBER 23

Boat and Engine Performance

For maximum speed, a boat bottom should be as flat as possible in a fore-aft direction

(longitudinally) for approximately the last 5 ft (1.5 m).

For best speed and minimum spray, the corner between the bottom and the transom should

The bottom is referred to as having a "hook" if it is concave in the fore-and-aft direction. A

hook causes more lift on the bottom near the transom and forces the bow to drop. This in-

creases wetted surface and reduces boat speed. A hook, however, aids in planing and re-

duces any porpoising (rhythmical bouncing) tendency. A slight hook is often built in by the

manufacturer. A hook also can be caused by incorrect trailering or storing the boat with sup-

port directly under the transom.

90-861326--1 MARCH 1999

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Critical Bottom Area

Sharp Corner

Transom (Stern)

Transom (Stern)

GENERAL INFORMATION

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