Belts and Hoses.
Any belts and hoses your outboard has have to operate in the brutally harsh marine environment.
Give them a glance once in a while, and heed the manufacturer’s schedule for their replacement.
If you find cracking or fraying, be safe and replace. Do not attempt to “flip” a belt in order to
extend its life, nor handle the belt with lubricant of any kind on your fingers. Keep these safe
from spray-on lubricants, too.
Tip:
Yamaha four-stroke outboard timing belts and HPDI
®
two-stroke outboard high-pressure fuel pump belts are
cogged and Kevlar
®
-impregnated, making them super-tough and non-stretchable. Still, Yamaha recommends they
be changed every five years or 1000 hours.
Spark Plugs.
As a general rule, pull four-stroke outboard spark plugs every two hundred hours or every other
season and check for proper color and wear. They should be a light brownish color and have
relatively sharp edges. When necessary, replace with the exact manufacturer and part number that
your outboard’s manufacturer stipulates. The brand type and style of spark plugs used in your
outboard are by design. They contain specific performance attributes that are engineered
into your outboard. Those little markings and numbers on your spark plugs contain a
wealth of information about heat range, thread depth, etc.; so don’t second-guess or
try to cross-reference here. Your outboard’s performance depends on it.
Thermostats and Pop-Off Valves.
These are responsible for regulating the operating temperature of your outboard. Simple and
effective, they’re best observed through any signs of change in the engine’s operating temperature.
Operating in saltwater can cause deposits to build up, causing the valves to stick open, which can
over-cool the outboard and prevent it from reaching proper operating temperature. Small bits of
debris in the cooling water can get lodged between mating surfaces and cause the same condition.
If this happens, removal and cleaning is most often the fix. Check your owner’s manual for specific
replacement recommendations.
Air Intake Passages.
Be sure to check the air intake passages for any obstructions such as bird nests and other debris
brought in by various critters. Look under your cowling, too. It doesn’t take long for your outboard
or boat to become home to local birds and bugs, and it can be a real headscratcher when it comes
to performance-loss diagnosis.
As a general rule, inspect the impeller and water pump assembly every year if operating in salt,
brackish or turbid water, and replace if necessary. The debris in these waters acts like sandpaper.
If operating in freshwater that is clear and clean, this interval may likely stretch to two seasons,
provided no dry operation has occurred. Be sure to check your particular owner’s manual for your
outboard’s specific service interval.
Note:
If you’re at all uneasy about performing impeller/water pump inspection and replacement procedures, have your
local Yamaha Marine dealer do the work. They have the tools, materials and training to do it right, for your peace of mind.
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