Why 50:1 and not 100:1

[anglingaddict]

In a recent post someone inquired about whether his older motor was 100:1 or 50:1? One reply said, "We've all gone back to 50:1 anyway..."<br /><br />Did I miss something? I have a 1991 Yamaha 4hp that is rated for 100:1. Is there a rule of thumb that when running an older motor you should switch to a mixture with more oil?<br /><br />Any and all thoughts would be greatly appreciated.

 

[ZmOz]

Re: Why 50:1 and not 100:1

Because 100:1 is not enough oil, period. Whether or not it can protect a running engine is up for discussion; however, one fact that cannot be denied is that 100:1 does NOT leave enough oil in the engine after you shut it off to prevent rust and lubricate during startup.

 

[DJ]

Re: Why 50:1 and not 100:1

The lack of an adequate protective oil film has pretty much been then reason.<br /><br />I imagine if you ran the engine every day for extended periods and it never sat very long, it would be OK.<br /><br />The manufacturers found it OK in durability testing. However, it is difficult to duplicate extended periods of off time.

 

[rodbolt]

Re: Why 50:1 and not 100:1

yep<br /> what DJ says. 100 to 1 will work fine for most small engines. a friend ran an 88 evinrude at 100 to one for a year until he told me. most engines yamaha makes under 40 hp can be safely run at 100 to 1. however it wont leave enough oil on the shiney parts to protect them during periods of storage. so the guy that uses it one weekend then puts it in the barn or parks it out back and gets busy may have a rusted motor come 2 or 3 months later. it happens, it happens a lot.<br /> good luck and keep posting

 

[anglingaddict]

Re: Why 50:1 and not 100:1

Thanks everyone!! I also did some browsing of the other forum areas and found extensive discussion on this topic.<br /><br />This website is such a great resource for everyone from amateurs to pros.<br /><br />Thanks again for your help!<br /><br />Tight lines.<br /><br />AnglingAddict

 

[gov2mod]

Re: Why 50:1 and not 100:1

My older Johnson 50hp was recommended to run 100/1. After the lower cylinder went I pulled it down to find the piston had self destructed due to lack of oil. My old 1978 35hp Evinrude has run <br />for years at 50/1 and never had a problem. I run<br />all of my outboards at 50/1 now even if they say 100/1. I'd much rather to have a little smoke than another ruined engine.