What should my mix be?

[Ripthemlips]

I have a I belive a 1956 Evinrude 35 HP motor 2 stroke what mix should I run on it. Ive heard alot of things 50 to 1 and 25-1.



Edit. Looking at online pics it seems it may be a little newer.

[Ripthemlips]

Also going to do a tune up and of course fresh gas.I hear people use seafoam to clear there motor out any details on that?

[billjr64]

I have a couple older evinrudes, was told to mix 40-1 due to wrist pin malfunctions, I did not listen though and have always mixed 50-1, no problems yet, I think you`ll foul plugs constantly with a 25-1 mix.

[Ripthemlips]

I have a couple older evinrudes, was told to mix 40-1 due to wrist pin malfunctions, I did not listen though and have always mixed 50-1, no problems yet, I think you`ll foul plugs constantly with a 25-1 mix.


yea the guy told me hes been running 25-1 but I was thinking to run 50-1

[Seahare]

The oil we used in the fifties was considerably different than today's oil. In the fifties (I was there) we used non-detergent 30W oil in the ratio of 1qt oil /6gals fuel(25:1).

Todays' oil is nothing like fifties oil. It's specifically formulated and has been extensively tested by the boating industry association (BIA) to be mixed in the ratio of one pint oil/ 6 gals fuel (50:1) and may be run at that ratio in any older motor that formerly used the 25:1 mix. Many people run their mixes at 1 pt. oil/ 5 gals fuel (40:1) due to two reasons: 1) Most 6 gal tanks never get completely empty and its easier to put in 5 gals with one pint. 2) They run their engines harder and feel more comfortable with a little extra oil mix.

FYI: BIA TCW-3 means Boating Industry Association Two Cycle Water Cooled Type 3.

[Ripthemlips]

Thanks for all the information guys. I am going to change the plugs get some fresh gas and decarb the motor using seafoam. Then I should be off and fishing in no time.

[ondarvr]

The older motors need more oil because they use bushings not needle bearings, the change in oil ratio was around 1964 when they had all (Johnson/Evinrude) switched to needle bearings.

While newer oils are better, the older motors still need more than 50-1. In the 60's all the motors I ran used 24-1 and there were no plug fouling issues.

[Seahare]

While it is true that there were outboard motors produced with plain metal bearings, they were made pre WWII and it's doubtful that any of these are in use today. Most antique outboards that haven't seen the junkyard now sit on a stand for display or are in someones storage and are never used or demonstrated.

Running an engine with too rich of a mixture is a waste and causes more damage than it prevents. All of the earlier engines use a deflector type piston and these are very inefficient. For every 10 gals of fuel/oil mix used, over 3 gals are dumped unburned because of the inherent incomplete combustion of a crossflow piston engine.

Using too much oil causes stuck rings, scorched piston skirts, and thick coatings of carbon on the cyl. head, piston dome, exhaust ports, and the underside of the piston.

In the sixties, two cycle oil didn't exist so gas was mixed with regular motor oil and the recommended mix was 25:1. With todays two cycle BIA TC-W3 oil, you may run at a 50:1 ratio.