2 stroke oil ratios

[machurley22]

Was surfing another forum (iboats - whisper it not) and came across <A target="_blank" HREF=http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=30;t=004187> this thread</A> which states flatly that 2T outboards should not use a leaner mix than 50:1 on the grounds that insufficient oil will otherwise be left behind to prevent rusting between operating periods.

This is a new one on me but is stated here with the force of unassailable fact. I've been running my 12yo Yamaha 8 on 100:1 (as recommended in the book) for the last two years with no (as yet apparent) ill effect and wonder what the panel think?

Dave

<hr width=100% size=1>

 

[sailorman]

i have reciently bought a Tohatsu 3.3. 50 > 1.
its the same engine as the marriner 3. something 100>1

<hr width=100% size=1>Nil iligitmo carborundum

 

[LORDNELSON]

The instruction manual for my Yamaha 2 recommends 1:100 for pleasure use and 1:50 for work use! I have always used 1:50 even though I am a pleasure user - on the basis that I would rather have too much oil in the mix rather than too little. Looking at the plug, exhaust gasses and the interface between the piston and the cylinder (when removing all the salt in the water passages) it would seem that there is a lot of oil around. However, the engine keeps running and the plug does not oil up. There seems a lot of latitude on the oil ratio and I can only assume that the engine produces a bit more power at the 1:100 oil ratio which is good for pleasure users but that for running under heavy load for long periods (work use) the engine needs the extra oil and would tend to burn it off more than my engine does. Certainly there is plenty of oil "left behind" with the 1:50 petroil ratio.

<hr width=100% size=1>

 

[jerryat]

Entirely agree! Far better to use 50:1 and put up with a little more smoke in my view. When I bought my Yamaha 2 'eggwhisk' a year or three ago, the engineer said 'forget the 100:1, if you want the engine to last, use 50:1, you won't regret it'. IMHO he's absolutely right. I increased the ratio on the earlier Mariner 2 and sold that engine in perfect working order 17 years later!!

Cheers Jerry

<hr width=100% size=1>

 

[Joe_Cole]

All I can say is that I've used 100:1 on my Mariner 3.3 and 8HP engines for 5 years now, with no problem.

Joe

<hr width=100% size=1>

 

[mirabriani]

Agree with Joe Cole. As previously stated I have used 100;1 on my Tohatsu 3 1/2
for three seasons. I must say it doesn't seem to like 50 ; 1
Lord Nelson makes a good point, if you work it hard you may need the extra oil
Oh and by the way I use fully synthetic moto cross racing oil.

Regards Briani

<hr width=100% size=1>

 

[ex-Gladys]

Funny, my 3.5 manual says 50:1.....

<hr width=100% size=1>Larry Botheras

Anderson 26 "Amber"

 

[rex_seadog]

The advice from Mariner's technical expert when I asked a similar question re my 6 year old 8HP is that 100:1 is OK when pottering around but that it's worth increasing to about 50:1 when running at full or near full throttle for long periods.

I believe the metering systems of oil injected 2 strokes operate on this principle.

<hr width=100% size=1>

 

[steve_l]

My '99 Mariner 4 Sailpower runs very nicely at 50:1.
However, the '83 Johnson 50 I also have since last spring suffers from chronic plug fouling at the same ratio. Going to try 100:1 in that next year...

-steve-

<hr width=100% size=1>

 

[machurley22]

"Oh and by the way I use fully synthetic moto cross racing oil."

I've been told that motorcycle oil is not suitable since it is designed for the much higher temperatures in a bike engine. Outboards run a lot cooler than bikes. This may have something to do with the problems you've had at 50:1.

Dave

<hr width=100% size=1>

 

[oldharry]

Chronic plug fouling is not usuallu an oil problem unless you are overdoing the oil, highly unlikely at 50:1. Two possibilities: 1 are you using a TCW3 grade oil? If not then you will likely get fouled plugs. 2: Use a hotter grade plug. If the oil is right then the plug you are using is not hot enough to burn the oil off properly under your operating conditions.

Personally I beleive that although engines will run 100:1, they are dangerously close to oil starvation at that mix, and the oil film is so thin that it is only just working, meaning that the bores and bearing faces will wear much more quickly.

With an engine used less than say 100 hours a year this is not noticeable until the engine is legitimately 'old', but an engine in daily use will wear out and not give a decent service life. This born out by Yams advice that a 'working' engine needs more oil. I would prefer to give the engine its best possible chance for a long life.

<hr width=100% size=1>

 

[aitchw]

<With an engine used less than say 100 hours a year this is not noticeable until>
<the engine is legitimately 'old', but an engine in daily use will wear out and not>
<give a decent service life.>

I tend to think it's more about the length of running time rather than total running time. So if you are nipping out to the mooring and back (10 mins) once a day for six days mix will be less critical than running continuously under load for an hour.

<hr width=100% size=1>

 

[snowleopard]

i was told by the service agent who sold me my mariner 3.3 that the 100:1 recommendation was made necessary by pollution regulations and that 50:1 was better for the engine. i generally use 100:1 but am always generous in the mixing as such a lean ratio leaves no margin for error.

<hr width=100% size=1>

 

[supermalc]

Just to mention all premix 2 strokes pass the petroil mix throught he carburettor. Increasing the ratio means less petrol, a weaker mixture. Not sure how significant this is, as my new Tohatsu 3.5 says to run in at 25 to 1 and then continue at 50 to 1.

I know the carburettor jetting was much more critical for my friends racing 2 stroke motorbikes.

<hr width=100% size=1>Malcolm.
<A target="_blank" HREF=http://geocities.com/malcsworld/>http://geocities.com/malcsworld/</A>
Take a look at my boating pages.

 

[jointventureII]

If you use the engine regularly then 100:1 is fine, but if it isn't frequently used, go for the 50:1 because it does help keep the cylinders lubricated

<hr width=100% size=1>

 

[oldharry]

BY 'engine in daily use' I mean working boats, where the engine may be clocking up 6 - 10 hours/day. In practice the 10 minutes a days engine will suffer more wear than in an hours hard run, because it is running cold so much of the time.

<hr width=100% size=1>

 

[aitchw]

Wasn't trying to pick holes in your argument or conclusion and agree about the high wear resulting from lots of cold running.

I totally agree about not running lean on lubricant. It can't do any good.

Plug fouling may also indicate poor mixture/volume control.

<hr width=100% size=1>

 

[machurley22]

Thanks to all who replied and shared their wisdom. I will increase my oil ratio as a result. My usage is a mix of predominantly ten minute periods (berthing and anchoring) with the occasional 6hr run (flat calm, got to get back for work). In fact I may well stick it in a bin and re-winterise with 50:1.

Thanks again,

Dave

<hr width=100% size=1>