1957 Evinrude 7.5HP Missing at low throttle

[smokin gun]

I've just restored a 1957 Evinrude 7522. I cranks on first pull, runs great at full throttle, but "misses" and eventually dies at idle.
I've watched a gazillion videos, reached out to some experts, but still haven't found a solution or a suggestion I haven't already tried.
Here is the run down.....
1. carbs completely rebuilt. Thoroughly. Many videos watched prior to rebuild.
2. fuel pump conversion installed (removed two line system). Pressure port capped off.
3. dialed in carb adjustment valves per Joe Reeves' guidelines. The high speed valve responds just as it should, and I was able to dial in easily. When throttle is backed of to idle, engine starts "missing" and eventually dies. There is no response from adjusting the low speed valve.
4. Fuel mix 32:1
5. Magneto completely gone through, parts replaced as needed, points set
6. New spark plugs and wires

At idle it will run for a few minutes while it's missing, however it will start missing more and more then eventually die. When it "misses" the motor jumps a little. I can throttle up at any point and it will again run great, then when I throttle down to idle it starts missing again.

I want to think it's a carburetor issue but since I rebuilt the carburetor thoroughly, I wouldn't know what else to do that I haven't already done. I also suspect it may be something in the conversion to the fuel pump, but I can't find any obvious problems.

If anyone has seen this problem I would love to hear how you corrected it.

 

[Crosbyman]

what is... I rebuilt the carburetor thoroughly .....

did you pull the top dime size plug and clean the low speed circuit incl. the VERY narrow side channel that sucks fuel from the lower carb bowl half. the upper half has a very small passage leading fuel to the top chamber wher the point LS needle allows fuel to enter the chamber with 3 small drip holes.

did you install enought packing on the LS sneedle

 

[brodmann]

There's two ways I know of to determine if it's a carburetor problem. First, when its missing, spray a little starter fluid into the carb and see if it picks up. The second one I've never tried, but I've seen it posted here and it seems logical, wave a slightly open, but unlit propane torch in front of the carburetor opening to see if it revs up. If increasing "fuel" makes it run better, then it's a fuel delivery problem. With that carburetor, you have to get a carb kit because you'll have to remove those lead plugs like mentioned above and the kit will contain replacement plugs. What's the compression on that motor by the way?

 

[Crosbyman]

seems the top dime size plug is generally aluminum whereas the actual lead plugs are BB sized inserts and used to seal certain passages normally not fooled with.. by me anyway.

 

[tphoyt]

I rarely ever mess with the lead shot either. I believe they are only there to fill ports that were made in the milling process and don’t really hold any debris. I had a hard time find those little bb’s once and ended up making my own by melting lead through a bronze screen and letting them drop into a bucket of water. After picking through all the drippings I found many that were just the right size so I’m set for life.

 

[Crosbyman]

I rarely ever mess with the lead shot either. I believe they are only there to fill ports that were made in the milling process and don’t really hold any debris. I had a hard time find those little bb’s once and ended up making my own by melting lead through a bronze screen and letting them drop into a bucket of water. After picking through all the drippings I found many that were just the right size so I’m set for life.

they only serve to plug things ... some JB weld would probably be good.

a bit of pre-stuffing follwed by a touch of baking soda and crazy glue will instantly turn it to stone like material.

 

[tphoyt]

Yea the super glue and baking soda is an amazing thing. I use it all the time for wood repair. I even did it in layers once and drilled and tapped and its still holding up years later.