Johnson 6hp won't throttle up all the way

[Perspective]

Motor: 1986 Johnson 6hp on a 12 Jon boat
Model: J6RCDE

My motor is running like it is rich, carb clogged, won't throttle up all the way, etc.

The history of the motor. I bought it a few years ago from a guy who had it in his garage for 20 years without use. It looked brand new, fired up and worked great so I purchased it. Has run really good for about 4 years.

Last year the power pack failed so I put a CDI power pack and spark plugs on and it was fixed. About two months ago my wife and I went for a drive and ran 3 gallons completely dry and the motor quit. No big deal we went for a nice little troll back to the boat launch. I got busy and finally put gas in it this past week and took it out. It fired up and I went for a drive to go fishing. It ran real slow and would die if I throttled down. A few times it would run uneven and start to speed up and then slow down. On the way back it got up to speed a few times after about 15 minutes and planed out but would be right back to running slow if I throttled down. It is almost like it is running cold.

At home I checked the plugs and they were black and oily. I pulled the carb off and took it a part and it was sparkly clean inside visually. I sprayed carb cleaner through all the ports and they flowed nicely. I did notice the little tube inside the float bowl broken so I thought maybe it wasn't picking up properly. After putting everything back together and replacing all the fuel lines I tried starting it in a bucket of water and it still runs the same and leaves a lot of oil in the water. I feel like it has too much oil but I have double checked my mix cup. I mixed 16 oz of xd30 with 5 gallons of non-ethanol gas. The only difference was that it was slightly lower octane than what I usually use.

Is it possible the thermostat is stuck open preventing it from heating up? Carb really isn't clean? Ideas.

I mixed the fuel 50:1 per everything I have read online even though the motor says 100:1.

Any advice would be greatly appreciated.

 

[oldboat1]

believe the little flex tube is required for proper feed — also need the small gasket under the nozzle well. The tiny high speed jet is screwed into the nozzle well, and the jet has to be squeaky clean.

First guess is that you sucked up something from the bottom of the tank when you ran it dry, but just a guess based on your narrative. Did you fully disassemble the carb? Best to soak it in some cleaner, then attend to all of the openings — top of the carb as well, under the cover.

50:1 is the correct ratio.

 

[Perspective]

Thanks! Yes I have new tube installed and the small gasket is installed. I'll try soaking the carb and see if this helps.

 

[F_R]

Make sure it is running on both cylinders. Could be as simple as a bad spark plug.

 

[JohnnyGuy]

Make sure it is running on both cylinders. Could be as simple as a bad spark plug.

Agreed. Your symptoms seem similar to when I had a fouled plug on my 15 last year.
Check spark with a gap tester and try some fresh plugs.

 

[Perspective]

Thanks for the suggestions so far.

Yep, thru some new plugs in it yesterday. Same. It really sounds like a carb problem because it dies when I try to idle and runs real chuggy and slow when WOT.

I thought maybe running it dry left some residual oil in the carb that gummed so I shot the ports in the carb with carb cleaner while it was disassembled. It seems like too much oil or something but I know I mixed 50:1.

Could bad coils or failing power pack cause this?The power pack is not even a year old and it's CDI.

 

[oldboat1]

Use a spark tester to check ignition condition. Set it for about 1/2 inch and work backwards until you find strong spark (around 3/8 inch minimum). If successful spark test, revisit carb work:

 

[F_R]

I don't know if you have a carb problem or not. I am trying to get you to narrow it down to that--or not.

Do this: Remove and ground one spark plug wire, then see how it runs. Then do the same with the other one. Results should be more or less equal. The carb feeds both cylinders equally, so if one is much stronger than the other one, it is not the carb. Could be a ruptured fuel pump diaphragm though. That is another test.

You did not use up all the gas and leave oil behind, or whatever you are thinking.

 

[Perspective]

So I couldn't find my spark tester but I did try pulling the plug wires one at a time. It runs the same speed on one cylinder as it does with two and it doesn't matter which one so I know I am getting a spark on both. I'm not ignoring earlier posts just trying what I can do at the moment. That being said, when I reconnected the plug wire the motor would increase rpms for a second from the unburned fuel caused by unplugging the wire. This leads me to believe it's a carb issue. Time for the acetone bath.

 

[F_R]

So I couldn't find my spark tester but I did try pulling the plug wires one at a time. It runs the same speed on one cylinder as it does with two and it doesn't matter which one so I know I am getting a spark on both. I'm not ignoring earlier posts just trying what I can do at the moment. That being said, when I reconnected the plug wire the motor would increase rpms for a second from the unburned fuel caused by unplugging the wire. This leads me to believe it's a carb issue. Time for the acetone bath.

Runs the same speed on one cylinder as it does on two?????

Whatever you say.

 

[Perspective]

Really, you can't tell the difference when one plug wire is pulled. It doesn't matter which one either.

 

[jimmbo]

When you say you mixed the oil into the gas, did you actually mix/shake/agitate the oil into about 2 gals of gas, then top the tank and agitate it some more? Or did you fill the tank and then pour in the oil?

 

[Perspective]

Hey jimmbo, I use a separate fuel can for storage. I filled it with fuel and then added the oil. Then I poured it into my boat tank. Then I said to myself, "you forgot to shake it" so I pumped it all (almost) back into my storage can. Finally I shook it up real good and then refilled my boat. I usually add the oil and then pump the gas. Ugh! Hmm!

I did get up to speed a few times after several minutes of slow boating.

 

[F_R]

Really, you can't tell the difference when one plug wire is pulled. It doesn't matter which one either.

That is really odd. Sorry, I don't have an explanation.

 

[oldboat1]

I did get up to speed a few times after several minutes of slow boating.

Encouraging, I think.

One of the tests for setting the idle needle is throttle up — not sure what yours is doing, but should be no hesitation or stalling.** Initial setting is 1 1/2 open, and adjust from there (try slowly clockwise first until it lean sneezes or stalls, then open it back up 1/4 turn.) Your idle air mix may be a little bit rich (too much fuel).

[Edit. **But should throttle up!]

 

[oldboat1]

http://ww2.iboats.com/Carburetor/dm/...iew_id.1546130

And…the roller has to contact the cam at the indentation/mark — carb throttle plate should begin to open at that point in the timing advance (the “link and sync”)

 

[Perspective]

So I think I may have figured it out. I was just inspecting the upper plastic part of the carb with high speed needle and noticed the high speed needle gasket had turned to mush. I am wondering if running it dry sucked a piece in or something. It's going to be a few days before I can test it but really appreciate you all letting me bounce my thoughts off and receiving the same from you. I will post again once I get the part.

 

[oldboat1]

(needle on top is an idle/low speed needle. The h.s. jet on the bottom is fixed.)

 

[Perspective]

Oh yes, thanks for educating me on that. Who knows. Well I fix that slow speed issue and see what happens.

 

[Perspective]

So I just realized that the gasket underneath the nozzle well is gone. I wonder if it slid out when the fuel ran out and tube broke. Somebody mentioned this earlier and I thought they were referring to the gasket on top of the nozzle well. Would this cause the problems I was having maybe?