What octane to use

[have boat will travel]

hi all, hope this is the right sticky. Wondering which octane is best for my 1994 Four Winn’s Sundowner OMC Cobra 5.0.

 

[alldodge]

That would be 87 octane

 

[boobie]

Agree, but non-ethanol.

 

[Bondo]

Ayuh,..... I agree, 87 octane is what's required, but I'm runnin' 91 octane, only because that's the only Non-ethanol gasoline available 'round here,.....

 

[Lou C]

Not only can't we get non-ethanol, but all the gas docks sell is 93 octane E-10, expensive, yes, but at least no real risk of fuel related detonation. Even my 30 year old piston tops looked quite good when I took it apart last year....

 

[HT32BSX115]

hi all, hope this is the right sticky. Wondering which octane is best for my 1994 Four Winn’s Sundowner OMC Cobra 5.0.

Howdy,

Try http://boatinfo.no/lib/omc/manuals/1986-1998omcmanual.html#/58 this manual is not bad but it may have some errors.....

The actual OEM manual covering your model would probably be the most accurate

Best way to determine would be to consult a service manual for your model engine since you could have one of the following in your boat.

502ACPMDA 1994
502AGPMDA 1994
50FACPMDA 1994
50FACPMDM 1994
50FAGPMDA 1994
50FAGPMDM 1994

502APLJVB 1993
502APRJVB 1993
502BPRJVB 1993
50FAPLJVB 1993
50FAPLJVN 1993
50FAPRJVB 1993
50FAPRJVN 1993


OMC did on some models specify different ignition timing to set depending on what fuel was being used. (more advance using higher octane)

More timing advance would produce a little more power but could result in detonation if you put lower octane fuel in it.

Don't hesitate to run E10 if that's all you can find...... It's what many of us have run since it's inception with no ill effects.

Cheers,

Rick