Trade-A-Boat – June 2019

94 | TRADEABOAT.COM.AU

Before getting afloat a few items should be
checked such as sufficient fuel and that the engine
sump oil level is where it should be. Also check the
prop is firmly attached so it won't deep six when you
go astern.

THE PROCEDURES
It's easy to understand that lot of people skip
reading the owner's manual in the excitement of
new machinery, but I was surprised to learn from a
Yamaha YouTube clip on running-in new four-stroke
outboards that this is actually quite common. This
is a shame as owner's manuals are a great cure for
insomnia. Sleep guaranteed!
After warming the engine in neutral at idle for
three minutes in warm climates and five minutes in
cold to fully circulate lubricating oil, idle the engine

in gear for around 15 minutes. Then for one hour

and 45 minutes increase the rpm to around 2000

(or one third throttle for engines not equipped with

tachometers). During this time vary the rpm every

10 to 15 minutes to help the piston rings bed in.

The only way to do this is by subjecting engines to

varying amounts of load.

Some manufacturers recommend taking the engine

to 3,000rpm (half throttle) from the first to second

hour but all are adamant that WOT should not be

used in this period. Again the rpm should be varied

every ten to 15 minutes.

From the second to third hour the rpm should

be increased to 4,000 (two thirds throttle) but again

not using WOT. The rpm must be varied as with the

earlier running-in stages.

After the third hour the engine may be operated

at WOT for up to five minutes at a time but reduced

back down to 4,000rpm for “cooling” periods of 15

or so minutes, right out to the first 10 hours. At this

time it's vital to check that the rpm reaches the upper

part of the manufacturer's recommended WOT rpm

range. For example, if the WOT range is 5,000 to

6,000 the engine should reach 5,700 to 5,800rpm

with normal hull loading.

The reason for under propping is the engine must

reach its peak torque band quickly to supply the

“grunt” needed to get a hull out of the hole. From

then upwards to near WOT the engine is under

less load. Fuel injected outboards will benefit under

these conditions because the electronic control unit

will only inject as much fuel as is needed, normally

resulting in excellent fuel efficiency from planing to

around 5,000rpm.