1955 7.5 Evinrude Gas/Oil Mix

[biloxiriver]

I have read with interest, some of the discussion on this topic but am still a bit confused. My 1955 7.5 Evinrude says to mix 30 wt oil at 1 qt to 5 gallons. That is what I have ran in it for the last several years and it runs fine at top end but doesn't idle smoothe. And, since it does smoke a bit at start up, I would like to know:<br />1. Can I, or should I, change to modern 2-cylce oil?<br />2. What ratio should I use using modern TCW3 2-cycle oils?<br />3. Could the oil be the idle problem? <br /><br />Can anyone help? Thanks much.

 

[alcan]

Re: 1955 7.5 Evinrude Gas/Oil Mix

Hi Biloxi<br />Run TCW3 at 24:1 and you will be just fine. The original specs called for Mobil outboard oil. They also recomended SAE30wt nondetergent in a pinch. Today there is no reason not to use TCW3. I doubt your choice of oil has any real bearing on your idle situation. My Guess is that it is time for a service/tune-up. If the ignition coils have never been replaced they are probably past do. Same goes for the points and condencers. Also remove , disassemble and clean the carb. Check all hoses for leaks. Now for the tank. If you are still using the old presure fuel system, carefully inspect for leaks. The two main places to look at are the o-rings in the fuel line connector and the rubber gasket in the gas cap. Your idle problem is probably do to ether crud in the carb or sucking or leaking air in the fuel system. Of course all this assumes that the motor has good compression to start with. Don't short the oil. One whole quart to six U.S. gals or five IMP Gals.

 

[steelespike]

Re: 1955 7.5 Evinrude Gas/Oil Mix

Alcan has you on the right track.<br /> In addition you may need to adjust the high and low speed mixture knobs.Adjust the high speed in gear at speed.and the low idling in gear.You may need to remove the knobs if you cant turn it far enough to get it to run better.

 

[Chinewalker]

Re: 1955 7.5 Evinrude Gas/Oil Mix

Don't run regular 30-wt. in it, as it doesn't burn well at all and leaves carbon all over the combustion chamber and rings. Do switch to TCW3 rated oil. Run it at 24:1 ratio and you'll be fine.<br />- Scott

 

[biloxiriver]

Re: 1955 7.5 Evinrude Gas/Oil Mix

Thanks for the response; all are appreciated. Will change to 2-cycle oil immediately.