40:1 ratio ok in merc 850 ?

[coolkook]

Just wondering if running mix at 40:1 will be ok..1977 mercury 850 85hp

 

[Alumarine]

If you're asking if it will cause harm to run a tank or 2 through, then no.
You should run it at 50:1 though.

 

[Texasmark]

I ran 50:1 (1 pint of BIA certified 2 stroke oil....TC-W3 today, to regular gas back then...unleaded today) in my 850 back when it was new. One of my best engines and I have had plenty.

 

[444]

I don't think you'll see any benefits to running 40:1. I've heard of some guys leaning theirs out from 50:1 all the way to 75 or 100:1. I've never tried it and just stick with the manufacturer's recommendation of 50:1.

 

[racerone]

At 40:1 you will not damage the engine.--------At 40:1 the motor will last longer .---At 40:1 it will smoke a bit more.----There are many motors from the 1950's still running fine on 24:1 mix so think about it.-----And the mixing of oil / mix ratios / and the lubrication inside the motor is not well understood by many folks.

 

[jimmbo]

There is no reason to run 40:1 if the engine is speced for 50:1. Bearings that run smooth with 50:1 are not going to run smoother with 40:1 or 25:1. OMC had a decrease in warranty claims when it switched to 50:1. They were getting fewer engines being damaged from pre-ignition because less oil meant fewer carbon deposits on the piston crown and cylinder heads, and less cylinder wall scoring/scuffing because of less carbon buildup behind the piston rings

 

[Texasmark]

Having run "Amalie, Better than it Has to Be"....automotive non-detergent motor oil.....to 6 gallons of gas because as the story goes OMC had some brass bushings in their engines and we didn't have 2 stroke oil available back then, and rather than needle bearings for the wrist pins and all, they used bushings that needed lots of lube any way....the reason for the 24:1 as I saw it.

Many 10's of years later, after having joined this forum and learning about Sea Foam (engine additive) and the "decarb" process, I don't put any more oil in my engine than is called for, with the exception of my last engine that had a variable ratio oil pump onboard and it ran 80:1 at idle up to 50:1 at WOT. So when I disabled it (10 year old engine and didn't want to trust it any more) and went to pre-mix like I had done all my life anyway, I had 50:1 at all engine speeds.

I agree with jimmbo!

Mark

 

[ondarvr]

It sort of depends on how you plan to use the motor.

For normal boating 50:1 is great ratio to balance lubrication and carbon build up, the more oil you add, the more build up you may get. If you ran close to wide open with the correct prop all the time it would see less build up, throttle down a bit and you won't burn off the deposits. Carbon build up is one of the leading causes of old carbed 2 strokes dying before their time, adding more oil increases the chances. You could de-carb the motor more often, but you aren't really gaining much on the better lubrication end of things. Sort of why they recommended 50:1 for normal use.