1964 1/2 Johnson 40 hp

wackostu

Seaman Apprentice
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Jul 18, 2012
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40
I have a 1965 Steury 15 ft runabout. She has a 1964 (mid year change) RDSL26S Johnson 40hp Motor. It has spark, and turns over and runs for about 5 seconds then quits. The plugs are new and gapped at .030. New gas and fuel line. Bulb gets firm. The automatic choke seems to be running properly. There is a rich/lean adjustment and a idle adjustment. Not sure where I should be set on those.

I have not checked the fuel pump or carbs. I would like some advise on what I could try that wouldnt put me into overoad, as this is my first time being a boat owner.

I am thinking I am going to have to pay to have the carb redone. I am first going to check out the secret file, but wanted to know if there was something easy I messed from the experts here.

Thanks in advance for your help.
 

F_R

Supreme Mariner
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Jul 7, 2006
Messages
28,195
Re: 1964 1/2 Johnson 40 hp

Like any other motor, it needs compression, fuel in the right amount, and spark under compression. Like any other motor, you must do some orderly inpection to isolate the problem. Check the compression. Then inspect the ignition system-- ("spark") means little or nothing. Old cracked coils will make a spark, but they won't run. Finally, take the drain plug out of the bottom/front of the carburetor and look at the end of it. Is it perfectly clean, or does it have a coating of varnish or goo on it? If the latter, the
 

wackostu

Seaman Apprentice
Joined
Jul 18, 2012
Messages
40
Re: 1964 1/2 Johnson 40 hp

Like any other motor, it needs compression, fuel in the right amount, and spark under compression. Like any other motor, you must do some orderly inpection to isolate the problem. Check the compression. Then inspect the ignition system-- ("spark") means little or nothing. Old cracked coils will make a spark, but they won't run. Finally, take the drain plug out of the bottom/front of the carburetor and look at the end of it. Is it perfectly clean, or does it have a coating of varnish or goo on it? If the latter, the

Is there a way to check compressions when the motor wont keep running? Where would I start with the ignition system? and I will take a look at the carb plug.
 

wackostu

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Re: 1964 1/2 Johnson 40 hp

I have a single flat head screw at the bottom front of my carb. Is this the plug referenced above?
 

lindy46

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Nov 27, 2008
Messages
3,886
Re: 1964 1/2 Johnson 40 hp

Screw is very small - maybe 1/8" in diameter. You check compression with the motor NOT running. Just crank it over with the starter for a few seconds. I ususally make sure there is NO gas in the motor, remove the plugs but leave the boots on and ground the plugs to the motor, then check compression one cylinder at a time. The plugs will spark, so if there is any gas in the cylinders, you can have a fire! Or just screw a spare spark plug in the open cylinder to seal it up.
 

wackostu

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Jul 18, 2012
Messages
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Re: 1964 1/2 Johnson 40 hp

Thank you. I will check for that screw. Your description helps!

If I had it set too rich or too lean on the low idle setting, would that make a difference in starting? As she was trying to turn over, if I moved the throttle to slow, the engine would backfire a little.

Maybe I am reaching at straws to do everything before an expensive repair. Looks like I need to find a compression tester.
 

lindy46

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Nov 27, 2008
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3,886
Re: 1964 1/2 Johnson 40 hp

Backfire, like out the exhaust? Or more like a sneeze? Backfire would indicate either a sheared flywheel key or plug wires reversed. Sneeze would indicate a lean running condition. Turn the slow speed needle counter-clockwise to richen the mixture.
 

wackostu

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Jul 18, 2012
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Re: 1964 1/2 Johnson 40 hp

More like a hiccup, if that makes any sense.
 

Alanhar

Cadet
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Mar 15, 2013
Messages
21
Re: 1964 1/2 Johnson 40 hp

I had the same problem and the fix is the reed leaf plates take them out and look if they are seating nice and flush without any gaps, all i done with mine was to bend them so they seated nice and flush and now my johnson 40hp starts first time and runs like new
 
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