1979 Mercury 40HP - Trouble running at idle...

[TheChad]

Hey all,<br /><br />I took this boat/engine out this last weekend for the first time...<br /><br />The engine will run fine at about 1/2 Fast idle speed, but when you bring the fast idle down below 1/2 the engine dies off..<br /><br />Also When you come off the throttle (Forward or Reverse) into nutral, it dies..<br /><br /><br />I'm sure its something easy... But I just don't know what to try..<br /><br />Thanks for the help..<br /><br />-TheChad

 

[andy6374]

Re: 1979 Mercury 40HP - Trouble running at idle...

Make sure the throttle shutters in the throat of the carbs are fully closed at idle. If not it was cause it to sputter and ultimately stall

 

[TheChad]

Re: 1979 Mercury 40HP - Trouble running at idle...

How do i check that?<br /><br /><br />Does anyone know the mixture settings on the carb?<br /><br />-TheChad

 

[Laddies]

Re: 1979 Mercury 40HP - Trouble running at idle...

Base low speed setting is 1 1/4, I usally start at 1 1/2 to 2

 

[TheChad]

Re: 1979 Mercury 40HP - Trouble running at idle...

Originally posted by Laddies:<br /> Base low speed setting is 1 1/4, I usally start at 1 1/2 to 2

The low speed setting is the screw directly to the right of the carb opening if you are looking at it from the front, right?<br /><br />You said you usally start at 1-1/2 to 2, do you go in or out from there?<br /><br />Thanks,<br /><br />-TheChad

 

[Laddies]

Re: 1979 Mercury 40HP - Trouble running at idle...

With the engine in gear at as slow of idle as possiable turn the screw in till the engine farts, that indicates lean then richen it just enough to get the smoothest idle possiable

 

[TheChad]

Re: 1979 Mercury 40HP - Trouble running at idle...

Originally posted by Laddies:<br /> With the engine in gear at as slow of idle as possiable turn the screw in till the engine farts, that indicates lean then richen it just enough to get the smoothest idle possiable

You said with it in gear, should that be done on the water (Under load), or am I able to make that adjustment with just a hose hooked up (No load)?<br /><br />Is there any other carb settings/adjustments to check?<br /><br />I don't have a tachometer so I guess I can't really check if the idle speed is correct...<br /><br /><br />Thanks again,<br /><br />-TheChad

 

[Laddies]

Re: 1979 Mercury 40HP - Trouble running at idle...

You can get close on a hose but not very good, it will change in the water as it will have back pressure and load both, which will throw the adjustment off--Bob