where to start on fuel system?

[chopper6322]

I have a 1990 Evinrude 70hp that idles very rough on muffs and shuts down as soon as i advance the throttle while in the water. I have between 110 and 115 psi on all 3 cylinders, the spark jumped the 7/16's gap on all 3 plugs so i'm down to fuel but not sure where to start, there doesn't appear to be any leaks, new boat side fuel lines and primer bulb, primer gets hard before the motor starts, and then just slightly softens when its running (which i believe is normal) I've replaced the pulse limiter and fuel filter on the motor and cleaned the carbs. adjusting the idle mixture screws seems to make no difference (they are currently set to 1 1/2 turns from seated) any ideas on where to start next? the link and sync. seems good according to the manual. what should i check next?

 

[WernerF]

I'm not quite sure for the 70hp carbs, but for the 60hp carbs the initial idle mixture setting is 2 1/2 turrn out.

 

[boobie]

Give the carbs a good cleaning and then adjust the mixture screws when the boat is in the water and in gear.

 

[emdsapmgr]

Trying to adjust the 3 carbs on this engine is tough. I know-I've got one. All three carbs are connected inside the intake manifold. As you make an adjustment to one, it actually affects all 3. Patience is a virtue in this case. Get the idle as best as you can in a general sense. Then start to fine tune it. Adjust one idle screw 1/2 turn or less, then wait 30 seconds for the engine to normalize. Then adjust the second carb. Etc. After seeming like eternity, you may start to see some idle improvement. Not an easy task, but do-able. Very much agree with boobie's comment.

 

[chopper6322]

Got it, I saw a video of a guy using Gatorade bottles with oil hooked to the primer line of the carbs on a snowmobile as a type of homemade manometer...would that be effective to adjust them? Also would running it in a Rubbermaid bin be equivelant to in the water or would the whole boat need to be in the water?