Regal 3300 Owner's Manual page 178

CHAPTER 6
Using Propulsion Unit Power Trim With Trim Tabs
N OTT: Illustrations show stern drives vs. outboard drive units.
Porpoising
Porpoising is a running condition where the bow "bounces" up and
down similar to a porpoise's swimming motion. This condition is
normally caused by the trim being too far "up" as indicated on the
trim gauge. Press "bow down" in one-half second bursts and the
porpoising should recede and the vessel speed should increase. Only
a small amount of "bow down tab" is normally necessary to make the
vessel bow actually go down.
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Adjust the trim tabs to achieve a
planing attitude. Use the power trim
to position the prop path parallel to
the water flow. At this point the trim
tabs may need a fine adjustment.
One advantage of the trim tab
system is that they allow trimming
of the hull while the power trim
results in trimming the props.