1965 Johnson 9.5 "cough" at low rpm..Help!

CaptainHook · Apr 16, 2010

I just picked up a really nice, clean 1965 Johnson 9.5hp. It has great compression, new water pump, brand new coils, points, and plugs. Starts 1st pull cold. Complete and really clean!! Got it for $90 and it runs great, that is unless you try and idle it.

It was "coughing" or something (I don't know how else to describe it) all the time. I swapped the carb with one from a 1973 9.5 parts motor I have and once I got the mixture set it was perfect. Ran it in the tank for about 30 mins with no issue.

Pulled the fuel line to let it run out and it started doing it again. Now it is fine with a little throttle or with the choke half closed but at normal idle it keeps "coughing" and will stall. Any ideas?

spunkyjr · Apr 16, 2010

Re: 1965 Johnson 9.5 "cough" at low rpm..Help!

Does your handle have a large round screw on it? This screws in and out to adjust the idle.

CaptainHook · Apr 16, 2010

Re: 1965 Johnson 9.5 "cough" at low rpm..Help!

It isn't an idle speed problem. It is some sort of carb issue I think. But how likely is it that I have 2 bad carbs?

jack20 · Apr 16, 2010

Re: 1965 Johnson 9.5 "cough" at low rpm..Help!

I'd try the mixture screw, if it runs good with a little choke then richen the low speed (turn out) usually a cough means its too lean

bktheking · Apr 16, 2010

Re: 1965 Johnson 9.5 "cough" at low rpm..Help!

spunkyjr said:
Does your handle have a large round screw on it? This screws in and out to adjust the idle.

65 doesn't have the adjustment on the handle unfortunately.

CaptainHook · Apr 20, 2010

Re: 1965 Johnson 9.5 "cough" at low rpm..Help!

I have tried and tried with the mixture and it just does not help!!!!! Other ideas anyone???

glassmaster68 · Apr 20, 2010

Re: 1965 Johnson 9.5 "cough" at low rpm..Help!

if it runs good with the choke on,,prob just dirty carb,if you have a bulb primer hose,make sure no air/fuel leaks

CaptainHook · Apr 20, 2010

Re: 1965 Johnson 9.5 "cough" at low rpm..Help!

With the choke on it seems to run good but the rpm's go up like I am throttling it or something.

glassmaster68 · Apr 20, 2010

Re: 1965 Johnson 9.5 "cough" at low rpm..Help!

yeah ,with the choke on it will make it pull fuel,,might be some trash in your low speed,causing it to lean out and cough,,,have you took the low speed needle valve out and checked the tip?if its leaning out be careful not to burn it up,it can burn a hole in your piston

CaptainHook · Apr 20, 2010

Re: 1965 Johnson 9.5 "cough" at low rpm..Help!

Yes, I had the needle out. I even switched to another carb. When I switched it ran great for about 30 mins and then started the same stuff!!!

kbait · Apr 21, 2010

Re: 1965 Johnson 9.5 "cough" at low rpm..Help!

You have 2 carbs that are clogged on the low speed circuit. You must pull the carb to clean.

ultra353 · Apr 21, 2010

Re: 1965 Johnson 9.5 "cough" at low rpm..Help!

Like Kbait said, probably both have clogged slow speed circuits. Or maybe a exhaust leak as these motors don`t idle well in a barrel. There is a brand new shift shaft boot and plate( which is no longer avail) on everyones favorite auction site right now with no bids if needed.

kbait · Apr 21, 2010

Re: 1965 Johnson 9.5 "cough" at low rpm..Help!

True that, ultra3. Run it without cowling to find that out. If that IS the problem, get the fleabay parts, as they're rare. I think it's a powerhead-pull job to replace

1965 Johnson 9.5 "cough" at low rpm..Help!

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