What octane gasoline

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Mike Ku

Cadet
Joined
Aug 28, 2001
Messages
17
I have an 18 hp, 1957 Evinrude Fastwin. Should I be using a high octane fuel in my two cycle mix or is regular unleaded 87 octane ok? Thanks, Mike :rolleyes:
 
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Dhadley

Supreme Mariner
Joined
Feb 4, 2001
Messages
16,978
Re: What octane gasoline

FRESH 87 only. Again -- FRESH!<br /><br />Good luck!
 
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nickster

Petty Officer 2nd Class
Joined
Jul 11, 2001
Messages
136
Re: What octane gasoline

Mike Ku! 87 octane is fine be shure to use tcw-3 (2cycle oil). 50-1 ratio, good luck with your motor.<br /><br />Nick
 
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BearcatMLA

Cadet
Joined
Sep 23, 2001
Messages
7
Re: What octane gasoline

I've always been told to run the best gas that I could... My dad has a 115hp Mercury that he has used at least twice a week(12-14hrs/day) since 1982 and it's never gave him any trouble... The boat was built here in town and when he took it in to get the power packs replaced they commented on how clean his engine was and advised him to continue burning the high octane gas. All that I can say is that it has worked for him for almost 20 years...so I burn the same in mine.<br /><br />B :cool:
 
JB

JB

Honorary Moderator Emeritus
Joined
Mar 25, 2001
Messages
45,907
Re: What octane gasoline

Mike, I wouldn't use 50:1 in that 1957 engine until you have gradually worked to it. <br /><br />OMC specified 24:1 when your engine was new. With modern oils and lead-free gas you can probably use 32:1 and MAYBE get away with 50:1<br /><br />Try the 32:1 first. Monitor it closely for power loss or overheat. If it performs well under load, then try a small amount of 50:1 under light load. Increase load gradually, carefully watching for problems.<br /><br />Bearcat,<br />The notion that premium fuel is "better" or higher quality than regular is a myth. It merely has extra additives to prevent knock in high compression 4 stroke auto engines. Those same additives can cause problems in 2 strokes that shorten engine life.<br /><br />Marine "white" gas is truly superior for 2 strokes, but its superiority comes from "higher" refining and absence of octane raising additives.<br /><br />Red sky at night. . .<br />JB :)
 
Chinewalker

Chinewalker

Fleet Admiral
Joined
Aug 19, 2001
Messages
8,902
Re: What octane gasoline

Hi Mike,<br /> Do NOT run your motor at 50:1 ratio. It has bronze bushings at the wrist pins and needs the extra oil to keep them lubed. It also has a bronze bushing under the center main bearing which acts as a compression seal between the top and bottom crankcase cavities. The oil acts as a sealant on the bushing, preventing blow-by. The tolerances in these old motors are much looser than new motors, so the oil does more than just lubricate the parts - it also helps keep things tight. 32:1 is as lean as I would go on the oil.<br />- Scott
 
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