40:1 PreMix 2001 Johnson 90 HP 2 stroke

[stewtn]

I just bought a pontoon boat with a 2001 Johnson 90HP 2 stroke. The previous owners at some point disconnected the VRO system and premixed fuel. They have labeled the boat to put 40:1 premix. However, 50:1 is standard. The boat started and ran fine. What should I be concerned with and what should I do now? go to 50:1 or stick with 40:1? Any advise would be great!

 

[jimmbo]

Welcome Aboard

50:1 is fine

 

[stewtn]

Thanks. Should I be worried about what the 40:1 mix did to the engine before?

 

[racerone]

No , at 40:1 the engine will be happy and last 10-1/2. more years than at 50:1-----Note how many engines from the 24:1 era are still running like new.

 

[jakedaawg]

Awesome racerone!!!

 

[Sea Rider]

40:1 will smoke worse than 50:1 and will foul plugs faster. if like boating at low speeds with 50:1 mixture, go for a wot spin for some minutes before taking toon back to port so OB burns oil build up on spark plugs's tips. Plugs will last longer.

Happy Boating

 

[flyingscott]

50-1 will NOT shorten your engine life by 10 yrs I dont' know why people say that. Oil has gotten better with time like everything else. What people fail to tell you is, A lot of the 50s engine designs were the ones that made the Transition to the 50-1 Mix. Those motors are still running like new also. 40-1 will not hurt your motor but 50-1 will be cleaner burning.

 

[stewtn]

Thanks Everyone!

 

[Scott Danforth]

50-1 will NOT shorten your engine life by 10 yrs I dont' know why people say that. Oil has gotten better with time like everything else. What people fail to tell you is, A lot of the 50s engine designs were the ones that made the Transition to the 50-1 Mix. Those motors are still running like new also. 40-1 will not hurt your motor but 50-1 will be cleaner burning.

He said motor would last longer at 40:1 than 50:1. most likely referring to extra lube. we all know motors are killed by lack of maintenance and dont actually wear out. lightly loaded you could drop down to 100:1

 

[Stumpalump]

No , at 40:1 the engine will be happy and last 10-1/2. more years than at 50:1-----Note how many engines from the 24:1 era are still running like new.

Pontoons are generally underpowered and overworked. 40:1 is what I'd run and if it's so underpowered it's running at WOT all the time I'd run even more. 100:1 is for idle and light loads and 16:1 is for max wot horsepower on a dyno. Most are someplace in the middle. I'm a little underpowered and run 40:1 because my motor has to work a little harder just like a pontoon usually does.

 

[flyingscott]

And with the last post the oil mix train has jumped the rails. I am out!!

 

[jimmbo]

The only time more oil was recommended by the engine manufacturers was during break in and sometimes in racing. In racing it was richer because race engines were run at higher rpms than stock and if the throttles were closed very quickly at these higher rpms the engine would be starved of oil. A richer mix provided a bit of a buffer allowing the engine a better chance of surviving those operating conditions.

 

[thumbnut]

I run 32/1 so there...yer all wrong...

 

[jakedaawg]

Thanks Everyone!

And you thought this was done:welcome:

Welcome to the forums by the way...we can have informative, well thought out discussions on just about any other topic. Oil and it's evil cousin the "ratio"---not so much.

 

[Sea Rider]

As long you have propped right your combo as loaded to run middle to max wot rpm factory range after break in period has ended, 50:1 is the way to go. At least on modern 2 strokes OB's that's what your fuel/oil ratio should be. 50.1 ratio is intended to run an OB for extended wot time periods with 0 issues. Just use a high quality 2 strokes oil.

All Owner's Manuals that have extensively read no one stated that OB's that works harder pushing heavier loads, applies for portable OB's as well, must use a higher oil mixture ratio. Check your particular OB Owner's Manual and prop it right.

Happy Boating

 

[racerone]

Lubrication in a 2 stroke is not well understood.-----At 50:1 there will be no issues.----More wear that you can not measure after one weekend of use.------Precision bits inside a motor will not wear as much with 40:1 ratio.

 

[Sea Rider]

A matter to tear both OB's powerheads down while one used 40:1 and the other 50:1 fuel/oil ratios, both with same exact run hours pushing same boat with same oil brand to make a fair comparison and internal wear evaluation.

40.1 ratio will foul plugs faster and increment carbon deposits on head, piston head and rings as well. On 2 strokes OB internals you'll find bearings, oil seals, metal rods, crank pin, apart from these, which other parts will enter in the precison bit category ?

BTW, this is just a friendly conversation with lots of speculation talk.

Happy Boating

 

[flyingscott]

Ok I am jumping back on. I will use my 60s personal motor as an example. My 1964 McCulloch 75 hp ran on 100-1 mix for its First 21 yrs. My dad bought the motor New in 1964 and ran only factory McCulloch oil and later Rooster tail from Texas. This motor was used exclusively for skiing and tubing. This wasnt the nice tubes that we have now this was a John Deere inner tube from a Tractor. Used a 1" hemp rope and made sure the valve stem was pointing down. My point being this motor was used HARD. In 1986 we went to 50-1 because the Oil was easier to find. This motor still runs like new with great compression. It also pulled 5 grown men up on skis couldnt steer but it did it. So I guess my point is using less of a good quality oil is better than more of a cheap oil. And according to some of the posts my motor should be worn out and in the scrap yd now.

 

[thumbnut]

I kinda figured ya would be back...

In a perfect world 50/1 is fine. Leave the tank vent closed and suffer a slow lean out the extra oil is helpful. Or a crank seal on one cyl starts to leak air and leans out but is not noticed.. Stuff like that..

 

[jakedaawg]

This is ridiculous ... we are talking 50:1 vs 40:1....negligible ...

let me state it different .02 vs .025. It's hard to measure the oil precise enough to know if your run 40 or 50 to one. We all pour the oil a little heavy anyways. I would guess that most of the cautious folks here run at 40 without even realizing it.

these are fun to watch though...

as far as fouling plugs? Not a chance with a properly tuned motor. That's not how the engine uses the oil...the oil mostly falls out in the crankcase and lubes bearings and whatnot then is burned up In exhaust, not in combustion chamber...that is why you get the black sludge dripping out of exhaust reliefs from time to time...