Why is my 110 Johnson misfiring?

AEROCOOK

Master Chief Petty Officer
Joined
Jul 28, 2004
Messages
872
First of all, I apologize for the long winded post, but I want to provide as much detail as possible.
Just got back from a week at the lake and Im looking for a little advice on diagnosing a stumble or misfire on my 1988 Johnson 110.
The motor runs very smoothly at idle whether in neutral at 750 rpm or in gear at 650 rpm and it also runs smoothly above 1800 rpms. The problem I have is a very distinct stumble or misfire when I accelerate from idle up to around 1800 rpm then as it passes 1800, it smoothes right out. So far I have performed a link and sync as detailed in my factory service manual, set the WOT timing using the Joe Reeves method, replaced the plugs, cleaned the carbs and still the problem persists.
Looking through the carb section in the manual I saw what were described as intermediate orifices and I am wondering what their specific function is? when I cleaned the carbs last year by soaking them in carb cleaner (a no-no according to the manual) I didnt access these orifices as they were concealed under the concave plugs and I didnt have new plugs to put in so I left them alone.
Any ideas?
 

Daviet

Fleet Admiral
Joined
Sep 24, 2008
Messages
8,958
Re: Why is my 110 Johnson misfiring?

They are kind of a carry over between low and high speed.
You might want to clean them.
 

AEROCOOK

Master Chief Petty Officer
Joined
Jul 28, 2004
Messages
872
Re: Why is my 110 Johnson misfiring?

They are kind of a carry over between low and high speed.
You might want to clean them.

Kind of what I suspected and I was hoping that someone would confirm it, thank you.
I will take the carbs back off next week, clean them properly and see if there is any improvement.
 

AEROCOOK

Master Chief Petty Officer
Joined
Jul 28, 2004
Messages
872
Re: Why is my 110 Johnson misfiring?

I ordered the plugs required to do the job but I have a question about sealing the plugs after installation. The service manual specifies some OMC product (of course) but there must be a suitable alternative right? Will loctite work? do I even need to seal them?
 

mamm7215

Petty Officer 2nd Class
Joined
Apr 28, 2010
Messages
184
Re: Why is my 110 Johnson misfiring?

You put them in round side facing you and with a 3/8" socket extension (use the solid end, not the female end), lightly tap the center using the socket extension and hammer. Lightly. You'll see the cap indent slightly. As it indents, it flattens and spreads sealing the port. Do this several times until the cap has flattened out but do NOT crack the cap or it's useless. I can't see these things being expensive, maybe buy a few in case you toast one.
 

AEROCOOK

Master Chief Petty Officer
Joined
Jul 28, 2004
Messages
872
Re: Why is my 110 Johnson misfiring?

You put them in round side facing you and with a 3/8" socket extension (use the solid end, not the female end), lightly tap the center using the socket extension and hammer. Lightly. You'll see the cap indent slightly. As it indents, it flattens and spreads sealing the port. Do this several times until the cap has flattened out but do NOT crack the cap or it's useless. I can't see these things being expensive, maybe buy a few in case you toast one.

Thanks, I appreciate the reply. I am familiar with the installation of the plugs, it's just that the service manual tells you to seal them after they have been installed. I need to know what product to use to seal them.
 
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