1978 evinrude 25hp idle and carb issues

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blaike.jones

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Hello all, first off I am new to the forum and I have been using this forum for months now in regards to fixing my other boat. This forum is the most helpful site you can go to boat repair related. So yesterday I traded my 1436 Dakota jon boat with a 9.9 mariner for a 1650 monark with a 78 evinrude 25hp. I got it in the water when I got home and the motor runs good. It's just the motor is really shaky at idle. I bought new spark plugs today for the cheapest start I could think of. I'm looking in rebuilding the carb next because today when I was messing with it I noticed when I squeezed the bubble on the gas line I had fuel leaking from underneath the carb. I can't tell if it's from the seals or the fuel line. Another question I have is is there something supposes to be connected to the lean rich nob from the inside. I look at it and it's just a rod that turns sticking through the plastic cover to the front. I don't see any way turning it could effect the carb because it goes to nothing.
 
Bosunsmate

Bosunsmate

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Re: 1978 evinrude 25hp idle and carb issues

The squeezing bulb leak might be from a failing float which pushes up against a needle that pushes into a ring seat to shut off the fuel flow into the engine.
If any of those parts a worn the fuel flow wont shut off when the carb bowl is full and it will overflow. It will also shake an run bad too
I think the lean rich nob on that pushes into a retainer washer and the needle at the end seats into the very end of the passage. You will need to screw that back in and then back it out a few turns. i dont know how many on that motor, someone else will. Getting that right can fix your shaky idle too
 
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blaike.jones

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Re: 1978 evinrude 25hp idle and carb issues

I was thinking something along the float issues. And the know. I'm not really sure what you mean. I'll have to take a pic because like I said. There is nothing on the inside of the cover connected to the knob
 
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Daviet

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Re: 1978 evinrude 25hp idle and carb issues

Trying to figure out the linkage problem, could you post a model number?
Have you preformed a compression test and checked the spark to see if it will jump a 7/16" gap and is bright blue?
 
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blaike.jones

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Re: 1978 evinrude 25hp idle and carb issues

So I took the carb off last night and checked everything out. Surprisingly the carb is as clean as any motor I've ever bought. The seal from the top cover where the float is is still in good shape as well as the float. I also found my leaking problem. It's the bottom fuel line. It seems to be a bit to big for the nozzle coming out. So my next question is will any kind of vacuum hosing work or is there some kind of special tubing I need to buy. It's only like 8 inches to the fuel filter.
 
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blaike.jones

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Re: 1978 evinrude 25hp idle and carb issues

I still need input on the linkage to the knob. I had a buddy look at it and he thinks there should be a linkage to the top idle adjust screw because it does have a white connecter on it
 
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racerone

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Re: 1978 evinrude 25hp idle and carb issues

Look for the linkage on a 1975 model motor.---------shop.evinrude.com
 
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blaike.jones

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Re: 1978 evinrude 25hp idle and carb issues

Well looks like I found it. #19 on carburetor. Unfortunately it's unavailable. Anywhere else I can find one
 
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