TRADEABOAT.COM.AU | 95
FEATURE | RUNNING-IN FOUR-STROKE OUTBOARDS
“Ten hours of
TLC are peanuts
compared to the
thousands of hours
of enjoyment
possible from
a four-stroke
outboard.”
LEFT TO RIGHT It's tempting to skip reading the
owner's manual of a new engine, but it's generally a good
idea; There's a visceral joy in throttling a four-stroke; Oh,
the place you'll go
So if your new outboard doesn't reach the upper
part of the recommended WOT range the prop
must be swapped for one of finer pitch. And on
the flip side if the rpm limiter frequently engages
(indicated by rough running as the ignition system
is interrupted) a coarser prop pitch is needed. These
changes need to be done ASAP, not when the engine
is taken for its first service, usually at 20 hours.
An exception to the under propping rule is when
an outboard is mounted on a displacement hull. The
hull doesn't have to climb out of the hole, so slight
over propping at WOT won't be detrimental provided
the engine is mostly operated at three quarters
throttle opening or less. For example, an Aqualine
F2.5 achieved only 5,000rpm at WOT on my
3.8-metre Fairlite Gull sailing dinghy, even thoughthe recommended range is 5,250 to 5,750. But at
three quarters throttle opening the rpm was still 4,500
with fuel consumption half of what it was at WOT,
indicating the engine load had fallen right off. Hull
speed fell only six per cent from 6.5 to 6.1 knots.THE WRAP
Always follow the running-in procedures outlined
in owner manuals and don't be impatient to get
through the running-in procedure. Ten hours of TLC
are peanuts compared to the thousands of hours of
enjoyment possible from a four-stroke outboard.
Life is a constant learning curve and the countless
number of outboards I've borrowed and owned,
run-in and evaluated over the past 50 years haveall
increased my knowledge and enjoyment afloat!