1977 Evinrude V4 115hp Fuel delivery/carb issue. Please Help!

[tawd77]

I have a 77 Evinrude 115hp V4 outboard. Since this is usually the first question, the compression is 120/120/120/90 - One cylinder has some scuffs causing the lower compression. That isnt causing the problem im having now though...

Here is the problem. The engine idles, but rough. off idle, it wants to fall on its face and die, unless you constantly tap the choke. Its acting like its starving for gas. Once you keep bumping up the throttle, and tapping the choke, you can finally shove the throttle forward, and it will run WOT flawlessly. If you back the throttle off a little, it still runs pretty good, and will return to WOT with no issues, runs great. But If you let the RPM's get down low, mid throttle or less, it will start running rough, and will need the assistance of the choke tapping to keep it running.

I pulled off the carbs, and they are perfectly clean. All passages/jets are clean. The linkages looked to be adusted correctly. There are alot of paint marks on the motor like it had recently been professionally rebuilt. So Im assuming the carbs are ok.

What else would cause this problem? My daughter is out of school in a week, and we need this boat for entertainment! Any help would be appreciated.

(PS. The bulb seems to stay firm, and the gas tank vent is open. Could the pump be the issue? If so, how would I test it? Thanks!!

 

[edfishing2]

Re: 1977 Evinrude V4 115hp Fuel delivery/carb issue. Please Help!

It seems that pump would be ok if running wot works. Perhaps you could adjust the idle screw up some.

 

[tawd77]

Re: 1977 Evinrude V4 115hp Fuel delivery/carb issue. Please Help!

I figured out that the gas tank was causing some of my problems. Cant fully test til I get the engine in the water with some backpressure, but it will now idle with the cold idle lever all the way down.

The engine still has this wierd ocassional misfire. I found a video of another evinrude 115 that sounds EXACTLY like mine.

In the beginning of this video, the engine runs pretty good, then sputters, then runs good then sputters. This is exactly what mine is doing. Sound like a bad coil?

http://www.youtube.com/watch?v=6s2owQgDl3A

At higher RPMs and WOT it runs smooth - Just does this sputtering smoking thing at low rpms like the engine in the video. I have cleaned carbs, clean gas/oil, and new plugs. Maybe something electrical?

 

[tawd77]

Re: 1977 Evinrude V4 115hp Fuel delivery/carb issue. Please Help!

I did some troubleshooting. I pulled out one plug at a time, and fired up the engine. If the number 3 plug is pulled, the engine will stay running with a constant misfire, like expected with only 3 plugs in, but runs steady.. If any of the other plugs are removed, it runs with a constant misfire, and still does this sputter/smoke thing. So, The problem seems to be with number 3 cylinder.

So, I switched the number 3 and number 1 coils around. The number 3 cylinder STILL has the problem. The coil is not the problem. So, would that be a problem with the power pack, or maybe the timer? If so, how would i test each of them?

 

[tawd77]

Re: 1977 Evinrude V4 115hp Fuel delivery/carb issue. Please Help!

Did some more troubleshooting. I switched the sensor 1 and sensor 3 wires around on the power pack, and then switched the 1 and 3 spark plug wires around. Now, those 2 cylinders are using the opposite sides of the power pack that the originally were. Number 3 cylinder is still the problem. So, the power pack is fine.

Now im down to the timer, or possibly a reed problem? Will the timer affect just one of the sensor outputs, or would it affect 1 and 3? there was 8.9 ohms between the 1 and 3 sensor wires from the timer.

If a reed was damaged, wouldnt that cause a compression issue in that cylinder? I do have a compression issue, but its in a different cylinder. The number 3 cylinder has 120psi.