50:1 is that ideal mix for all rpm's

[spete]

Just wondering if pre-mixing at 50:1 gives your engine the necessary lubrication at high rpms? I'm assuming that oil injection systems give more oil at high rpms and less at low? This all comes back to the question to keep an oil injection system hooked up or disconnect and premix. I know that many an engine has been run with pre-mix and operated great for many years of service - just wondering if i should disconnect the oil inject on my '98 Yamaha to avoid any blow ups down the road due to mechanical malfunction and if that will create unecessary wear and tear on engine parts?

 

[Forktail]

Re: 50:1 is that ideal mix for all rpm's

The Precision Blend oil injection system on your 98 is very reliable. It makes no sense to disconnect it. In fact you can actually damage some engines because the oil injection pump is driven by the engine and it's lubricated by the oil itself. A pump run dry can seize up.<br /><br />A 50:1 mix would be ok assuming you use a quality TCW-3 oil. Oil injection systems give more oil at higher rpm because there is more fuel and air being used. Less oil at idle speeds because there isn't much fuel and air going in. The pumps are calibrated very accurately with regards to fuel usage or throttle position.

 

[spete]

Re: 50:1 is that ideal mix for all rpm's

Thanks Forktail for the opinion ... this gives me a bit more confidence in the Precision Blend system I was considering disabling. I wasn't aware of the pitfalls to disconnecting - my line of thinking was as the odds of mechanical failure increase with time why not eliminate a system that seems to fall into the "overdesigned" category and not really necessary when you can pre-mix.<br /><br />Thanks again

 

[JB]

Re: 50:1 is that ideal mix for all rpm's

Howdy, SPete.<br /><br />Forktail's input is not just opinion. It is mostly fact.<br /><br />While it is true that disconnecting a reliable variable ratio oil injection system (Not VRO. That was OMC's name for it.) compromises ideal mix and therefore probably increases carbon, smoke and other disadvantages of an oil-rich mix at low rpm, even the Yammy Precision Blend system can fail.<br /><br />In the balance, ideal mix vs. fail-safe mix is a decision that changes balance depending on the reliability of the system.<br /><br />I never heard of a Yammy, Suzuki or Tohatsu system failing, but I have heard many sad tales of VRO failing and failing to warn the user in time to save the powerhead.<br /><br />I agree with Forktail on the Yammy. Keep the Precision Blend.

 

[jim dozier]

Re: 50:1 is that ideal mix for all rpm's

In addition to the comments made above, I think you will find that you buy less oil with the Japanese injection systems. They had years to perfect them on motorcycles. My manual (for Suzuki) says that the injection system is approximating a 50:1 mix at high engine speeds and about 100:1 at idle. This results in less fouling at idle and less oil used than a constant 50:1 mix at all times. The 50:1 concentration in oil/gas mix was arrived at to cover the maximum lubrication need of the engine not the minimum.

 

[spete]

Re: 50:1 is that ideal mix for all rpm's

I'm getting excellent info on this board - thanks for all the opinions. Will keep the P-B system intact and hope that if there ever is a failure I get a decent warning in time to save the motor.

 

[BillP]

Re: 50:1 is that ideal mix for all rpm's

Also note that OMC did a few years of 100:1 ratio (non vro) outboards and used the same IDENTICAL powerheads as their 50:1 ratio engines. There is more to this but the moral of the story is there is a huge safety margin built into the 50:1 mix. The reason omc stopped 100:1 was corrosion (not wear)on engines that sat for long periods...the 100:1 didn't leave enough coating on the internals so they went back to 50:1 and the problems ceased (for the most part). This was told to me by the OMC International warranty mgr for S.America, Bahamas and Bermuda. He also told me that the engines needed only 150:1 for lube properties at max throttle and load.

 

[spete]

Re: 50:1 is that ideal mix for all rpm's

Very interesting - probably a blessing to those who have had a half tank pre-mixed in the boat and top 'er off with forgetting the oil. Good to know.

 

[CKJR]

Re: 50:1 is that ideal mix for all rpm's

my recent conversations with tech support at johnson confirms this. the tech indicated that all is needed is 150:1 (new motors are run at WOT at this ratio with no damage) the problem arises when a motor is idled down a canal and parked for several weeks. the light oil mixture is not enough to prevent rusting of internal parts over several weeks. the new johnson motors are a constant 60:1 ratio for this reason.