August 16, 2010

MEMORANDUM

TO: EPA Docket #

FROM: Cheryl Caffrey, Mechanical Engineer, ASD, EPA

RE: Comments on Yamaha Website regarding Yamaha engines and ethanol blend fuels 

_____________________________________________________________________________________

Issues with ethanol fuels are known by the boating industry and are represented by 

information found on the Yamaha website www.yamahamotor.com/outboard/faq/viewfaqanswer. Examples of questions and answers from the 

website are listed below.

Question

Why do boats seem to have more issues attributed to E10 fuel than 

cars?

Answer

Cars are having issues but are somewhat more tolerant due to typical usage patterns and differences in their fuel 

systems. Major differences are: 

• Modern automotive fuel systems (fuel filler, fuel tank, distribution lines and engine components) are closed or 

non-vented. Once the fuel is pumped into the tank, there is very little circulation of outside air (containing 

moisture) into the fuel system.

• Boats are operated and often stored in a very wet environment increasing the risk of water directly entering the 

fuel system. 

• Boats have vented fuel systems which allow moisture laden air to circulate into the fuel tank as the fuel is drawn 

out of the tank and as the fuel expands and contracts during heating and cooling cycles of the outside air. 

• Automotive fuel tanks are typically much smaller than boat fuel tanks and are refilled more frequently. A full tank 

of fuel in a car or truck, typically 20 ~ 40 gals, may be used and refilled every week or two. Boat fuel tanks, 

typically 40 ~ 100+ gals per tank, may only be refilled once a month during the boating season and typically may 

sit unused for many months during the off season. 

• Some boats use fiberglass fuel tanks. Polyester resins can be dissolved by ethanol.

Question

Wouldn’t the cleaning properties of ethanol be good for a fuel system?

Answer

No, fuel systems that have been used for non-oxygenated gasoline will have varnish depos¬its and surface 

corrosion (rust and aluminum oxides). This includes the tanks and pipes used for fuel storage and 
transportation. Ethanol will clean varnish as well as surface corrosion from any surface it contacts. Ethanol 

may dissolve plastic resins used to make some fiberglass tanks. The amount of material cleaned from all of 

these systems can quickly exceed the filtration capacity of fuel system filters resulting in restricted fuel flow. 

Ultimately engine perfor¬mance is reduced and potentially damage to the engine can occur. 

Question

Are Yamaha engines compatible with E10 fuel?

Answer

All current models as well as most engines built since the late 1980’s have been designed with fuel system 

components that are tolerant to fresh fuel containing ethanol up to 10% (E10). Outboard fuel systems can still 

be affected by: water, dissolved gum, varnish, corrosion particles, and dissolved resins that E10 fuel has 

cleaned from the distribution system and your boat’s fuel tanks.

Question

Can I use fuel with a higher percentage of ethanol, such as E15 or E85?

Answer

No, all of the negative issues discussed in this FAQ section will be increased and may cause major damage to 

the engine.

Question

Does Yamaha make fuel additives to combat problems related to the 

ethanol in E10 fuel?

Answer

Yes. We have two fuel additives: Ring Free PLUS and Fuel Stabilizer & Conditioner PLUS. The “PLUS” includes 

reformulations for our standard Ring Free and Fuel Stabilizer & Conditioner. 

The Ring Free Plus protects against the corrosive affects of sulfur salts in E10 (10% ethanol-blended fuel) on 

electronics parts and fittings in the fuel system. It is highly recommended for all electronic fuel injected engines 

(EFI). The Fuel Stabilizer & Conditioner PLUS helps protect fuel system metals affected by E10, helps to prevent 

fuel oxidation that results in gums and varnishes and keeps fuel fresh and potent up to year of storage. Fuel 

Stabilizer & Conditioner PLUS is recommended to be used at every gas fill up, not just for storage.