outboards at 50:1 now at 100:1, why?

[1 FMF]

correct me if my impression or memory is wrong, but hasn't all 2-stroke outboards more or less run at a 50:1 ratio?

I bought a 2006 yamaha outboard, 25hp, and it says plenty of places on it for 100:1 ratio.

so my questions are, what changes were made to the engine if any that now allow for a 100:1 oil ratio?

does anybody know when the big push to 100:1 started?
It would be cool to see owner's manuals for the last 5-10 years maybe and see where 50:1 changed to 100:1. If that is the case, then I'd like to know what changed.

Has the oil really changed? I've been running on the same 5-gal jug of stuff for small outboards for the last 10 years so I haven't really paid attention to the oils. I run yamalube 2-M now on my outboard, was there a yamalube 2-L or something that wasn't good enough to run at 100:1?
Give me something that makes practical sense, because it so far is sounds no different than the push to lighter viscosity 4-stroke oils for fuel economy.

 

[TimVipond]

Amsoil has had a synthetic 100:1 outboard oil since 2004.

 

[dwendt44]

Improved oil is the main reason for the shift.
Two cycle engines, at least the quality ones, are properly machined and well cleaned before assembly, and designed to work at that ratio of oil mix. Most are oil injected these days.
Mercury Marine started the 100:1 quite a while back, but discontinued the oil. Cost at the time, and some owners with older motors found that their engines weren't up to it for that ratio of oil. The 100:1 ratio oil worked OK in oil injected motors, not so well in pre-mix.
If the engine and/or owner's manual says 100:1, use only a quality oil at that ratio.

 

[Master ACiD]

improved oil? sence when? tcw3 has been around for a while now and its the same old oil its awalys been.

i think the 100:1 is purely to reduce pollutiona nd emissions ast the cost of engine life. if run it at 50:1 if you do any sort of extended or hard running.

 

[Lonnie]

Boat owners are being asked by the manufacturers to give up the life of their engines to the cause of smog control, or go to a high quality synthetic and pay attention to the operation of there engines. For years boats got away with cheap 2-stroke oil because smog conrol was not a problem and the ocean or lake they operated in was like a great big radiator. Out of this you may get an engine that runs cleaner but you'd better pay attention.

 

[wileyE]

Many of the manufactures that "allowed" 100:1 either moved away from it or stated in the manual that it did not leave sufficient oil in the motor for storage. Most auto-mix setups are set to average 50:1, and most tcw3 oils are blended for 50:1 (tcw does 1 test at 100:1) The variable injection pumps will go down toward 100:1 (or lower) at idle or troll speeds. None would allow full throttle that way. Small troll motors that putt putt all day do fine on 100:1, you just wouldn't want to run em wide open or try and store them for a month after running 100:1.

 

[lazaro]

I have used 100:1 ratio in my 1100cc jet ski for 7 years with no problems and have various freinds that use it also in their outboards with no issues, yes I agree it may not seem like enough oil but past performance and teardowns have proven us otherwise...

 

[wileyE]

Quote:

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I have used 100:1 ratio in my 1100cc jet ski for 7 years with no problems and have various freinds that use it also in their outboards with no issues, yes I agree it may not seem like enough oil but past performance and teardowns have proven us otherwise...

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I betting you used amsoils 100:1 oil NOT amsoils other product that is formulated around the 50:1 spec most outboards use. Only post because I think the needs to be a distinction.

 

[oilboy123]

The Amsoil 100:1 oil is definitely more concentrated. So it will have a better protective film.