1956 30HP Evinrude Big Twin -- What Gas:Oil Ratio is really best??!??!?

I am the proud new owner of a 1956 Evinrude 30HP Big Twin. I've cleaned her up and she's running pretty well (a little rough on the low idle, but I'm more than satisfied at the high end).<br /><br />Here's my question: The decal inside the bonnet calls for a 24:1 gasil mixture. So does most of the original literature I've found on this motor.<br /><br />But my local mechanic (who's been in business for decades and knows OMC products inside and out and whose opinion I generally trust) says, "Nah. Run it at 50:1." He says that modern outboard 2-cycle oils are a lot better and that it will be just fine at 50:1, with less plug problems and less smoking.<br /><br />So far, I've compromised and run about 10 gallons through it at 32:1. The motor seems happy. It's not overheating, starts on the first try everytime, and the smoke level seems fine.<br /><br />But am I running a risk of damaging this fine old piece of equipment? I'd like to hear from folks who have experience with this or similar engines.<br /><br />Thanks!

Re: 1956 30HP Evinrude Big Twin -- What Gas:Oil Ratio is really best??!??!?

My parts books only go back to 1957, so I can't be sure about your engine. However, the '57 Big Twins did have roller bearings, which would allow a ratio above 24:1.<br /><br />There have been hundreds of opinions on this issue. I would stick with 32:1 if I were you. If you find out that your '56 has friction bearings, then definitly don't go higher.

Re: 1956 30HP Evinrude Big Twin -- What Gas:Oil Ratio is really best??!??!?

I wouldn't go any leaner than 32:1. Better oils, yes, but those old motors still need a fair amount of oil for sealing purposes. The center main is kind of a combination roller and bronze deal and needs the oil to keep it happy...<br />- Scott

Re: 1956 30HP Evinrude Big Twin -- What Gas:Oil Ratio is really best??!??!?

I've been running 32:1 with TCW-3 oil, sometimes erring on the richer side, with a '57 Evinrude 7/12 and a 35. Both run well. If the carb is clean and everything is properly adjusted, the rich mixture works fine (as intended). If you are running the 30 in a barrel, the water will heat up and you won't be able to dial in the idle properly -- and can overheat the engine if running up the rpms. I think it's normal for the powerhead on the 30s and 35s to jiggle around some at idle.

Re: 1956 30HP Evinrude Big Twin -- What Gas:Oil Ratio is really best??!??!?

The '56 30hp had rollers on the crank but the wrist pins did not. While 50:1 will generally work OK, you are safer running with a heavier ratio. I have the same motor as yours in the Johnson flavor. I run mine at 32:1. I think this is a good compromise between the original mix specification and the improvments in oil. So far it's worked well for me...

Re: 1956 30HP Evinrude Big Twin -- What Gas:Oil Ratio is really best??!??!?

Thanks to all who responded! As someone noted, there have been a lot of opinions about this issue. I'm going to stay in the 24:1 to 32:1 range rather than risk running this gem at 50:1.

Re: 1956 30HP Evinrude Big Twin -- What Gas:Oil Ratio is really best??!??!?

Hey Milo....<br /><br />The guys gave ya' some sound advice and staying in the 24:1 range will give the old girl extra life. Just remember to decarb once in a while. Keep the innards clean.