Idle speed for 50’s OMC’s ?

[bob-d]

Just picked up a tiny tach, and was playing around with the idle on my 58 10HP Johnson. It ran pretty well at about 500-600 RPM.
Look arounded in several service manuals, but haven’t seen a definitive number that the factory said to use (or shoot for).
Anybody have any ideas?
Bob D

[dan-in-tn]

That sounds pretty good. To me it is a matter of personal preference? Do you want the motor to shut off when you close the throttle or do you want to push the stop button to kill it? You can set the idle stop screw so it won’t die till you push the stop button. It’s what ever you prefer? Those old motors will get down & purr.
It’s before they worried about every ounce the motors weighed. Heavier flywheels help keep a motor going between power pulses. I’m sure other things factored in also, but today’s engines just don’t seem to place valve on a really low idle. JMHO.

Dan in TN

[frankr]

I love it when they’ll get down around 500 rpm. Not many can do that. An old Scott or Champion single can do it with ease.

[frankr]

Speaking of heavy flywheels and slow rpm:
https://www.youtube.com/watch?v=Hp71aLTKBRk

[lindy46]

quote FrankR:

Speaking of heavy flywheels and slow rpm:
https://www.youtube.com/watch?v=Hp71aLTKBRk

I don’t know the RPM’s but my little 1958 Lightwin will tick-tick-tick along sort of like that video – it idles so slow that the boat barely moves. I use it like an electric trolling motor when I’m fishing. 🙂

[RICHARD A. WHITE]

I know of a Caille that can idle at 160 rpm, and my Evinrude I have had it under 300 rpm.
I do know that use of the timing tool will help get that as low as the engine can go, so long as the carb is adjusted while idling down….

http://www.richardsoutboardtools.com
classicomctools@gmail.com

[vintin]

Even using the timing tool the lowest I can go with my 1957 35hp Johnson is 650 to 700 and happier at 800rpm.

[bob-d]

I had it down to 450 but it was starting to stumble, and yes by the way, I did use Richards tool to time it.
Bob D

[chris-p]

650 to 750 under load in gear is about right.

[Author]

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