oil mix

[seahorse5]

I'm with Joe Reeves as I remember a bulletin about changing the oil mix on older motors. I thought it came out around 1966 or so when OMC came out with their own outboard oil. Back then it was "certified" by the BIA, the forerunner of NMMA.<br /><br />If I remember correctly, it was for 18hp and up ( or 10hp and up) motors could run 50:1. The old 3hp was all bushings, as was the 5.5 and the infamous 'rod-throwing' 7.5 hp models and those were kept at 24:1.<br /><br />Many of the early and mid-'50s motors used 16:1 - 1/2 pint per gallon.

 

[rickdb1boat]

Re: oil mix

Seahorse<br /><br />So is it 1966 and up Models 10 HP are the only ones that can be safley run 50:1? And all the others from 1965 and below, must run a richer oil mixture?

 

[JB]

Re: oil mix

Prior to 1964 OMC recommended 24:1 in ALL engines. <br /><br />1964 and later engines can use 50:1 after break in with 24:1

 

[rickdb1boat]

Re: oil mix

Gottcha, JB. There's just so many different opinions and experiences on here , it's hard to tell on these old dogs. But did they not make some smaller engines with roller/needle bearings before 1964? I know what you are stating is what is recommended by OMC...

 

[JB]

Re: oil mix

Hi, RB.<br /><br />Some of the pre-'64 engines had "frictionless" bearings on the crank and big ends of the rods, but still used sleeves on the small ends of the rods.<br /><br />I have always found it a bad idea to second guess the manufacturer's engineers.

 

[rickdb1boat]

Re: oil mix

Thanks JB! I'm gonna follow that advice when others ask from now on. To many descrepencecies to guess at what uses what.<br /><br />Thanks,