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My Johnson AD-10 owners manual says to use a 1:16 mixture. Yet I came across this common parts list from 1964 which mentions 1:24.
I’m aware of the brass bushings and pros and cons of using these mixtures but I was wondering if anyone of you has actual experience with running these engines on a 1:24 mixture?
Well, it is up to you. Personally, I disagree with this recommendation, especially on the 7.5hp models, which are more prone to rod failure. I know, today’s oils are better, true enough. But, they are not that much better. The beauty of these engines is when they are in good tune, they hardly smoke at all, even at 16:1
Stick with the original 16:1 recommendation…
As the years went by and consumer pressure mounted I am sure that there was “pressure from within” at all the outboard manufacturers to ease the oil mix requirements on their engines.
One only has to look at OMC’s decision to recommend 100:1 for a while; before they started getting a bunch of warranty claims for blown powerheads.
I would (and do) stick to the original manufacturers recommendations on the 50’s engines .
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In 1971 the factory oil recommendations were updated again to 50 to 1.
To answer your question as to do people actual reduce the amount
of oil they run, I do. I run 3 oz per gal. (about 42 to 1) in most all my
motors and have been since the late 90’s.
Below are some I have on You Tube. The first one, 1928 Elto Speedster
is basically a parts built around 25 years ago to answer this question
for me. I don’t run it every year but when I do I’ll put between 45 to 55
gallons of fuel through it. All the motors posted on You Tube I have had
on a boat for a least a month except for the 1938 Mate. Most have made
it to the lake more than 1 summer. Most of my motors are pre. WW-II
bushing motors.
This is how I chose to find the answer to that question. I’m not trying
to tell anyone how much oil they should run. Just offering my experience.
Tubs.
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More oil is cheap insurance. I use Walmart house brand (Super-Tech) outboard oil that is TCW-3 rated. It’s usually not on the shelf with the name brand oils, but at the end of the aisle on the bottom shelf – I buy it in gallon jugs. I run my 24 to 1 and 16 to 1 motors at 20 to 1, because it’s convenient to dump a quart of oil into a 5 gallon can of gas and then top off the outboard tanks from that. I run my 50 to 1 motors at 40 to 1, putting a pint of oil into 5 gallons. When I run a motor on a homemade 8 foot hydroplane, since it is revving above max rated RPM, I double the oil.
Dave
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