Yamaha V-MAX SHO VF250 Maintenance Manual page 8

What is "dry corrosion"?
What causes it and what can I do about it?
Dry corrosion occurs in areas not in direct
contact with water—exhaust systems, for
example. The outside of most exhaust system
components is cooled by raw water to prevent
overheating. When today's ethanol-enhanced
fuel is burned, it creates by-products known as
sulfate salts. These salts are highly corrosive,
especially when exposed to very hot temperatures. If the outboard's cooling water passages are not
kept clean by regular flushing (the exhaust area in this example), hot spots can form on the interior
of the exhaust components, concentrating the sulfate salts' corrosive effects. In effect, it's corrosion
from the inside out. That's why flushing your engine with fresh, clean water for 15 minutes after
each trip is a vital part of preventing even dry corrosion. It helps the cooling system run at maximum
efficiency by keeping the cooling water passages clean and clear, which helps minimize the heat
inside the engine, making it less susceptible to dry corrosion.
How can I fight corrosion on the outside of my outboard?
It's a good practice to set up a regular schedule and stick to it. There are quick and simple things you
should do after every use if you boat in saltwater, and periodically if freshwater is your game. These
include visual inspections you should do every time.
If you're unsure about what to do and when, your
authorized Yamaha Marine dealer can help.
1
Rinse it.
• Don't spare the hose when returning from a trip, particularly in saltwater. Rinse the
entire outside of the outboard with clean water. Give it a once over with some mild soap like
Yamalube Wash & Wax Concentrate and a soft cloth while you're at it (do not use liquid dish
®
detergent—it can strip off important protectants). Go ahead and wash the whole boat and
trailer. Wiping it down with a good quality chamois afterward helps keep it all looking sharp.
8
Note: If salt build-up has become a problem, or your outboard's powerhead has somehow
been directly in contact with saltwater, it's okay to gently rinse portions of the powerhead with
clean, fresh water to remove salt and other nastiness. Just use a hose on low pressure—not
a spray attachment—and don't rinse around the air intake area. Rinse out the inside of the
cowling, too. Make absolutely sure both the powerhead and the cowling are completely
air-dry before re-installing the cowling.
2
• Spray it.
a protectant like Yamashield.
displacement agent and a corrosion preventative all rolled
into one. A high-quality silicone spray works well here, too.
Spray all external powerhead surfaces and the electrical
connections to help keep them corrosion-free, and the
rubber cowling sealing gaskets to help keep them supple
and effective at sealing out harmful water.
Scan here to see a video
about corrosion prevention.*
Liberally spray the entire dry powerhead with
It's a lubricant, a water
™