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Overhauled 1956 7.5 Fleetwin surges and stalls... ideas?

L

lake_trout

New member
Hello! New guy here. I've been fixing old junk and small engines since I was a kid, but outboards are a new hobby for me. I overhauled an abandoned 1956 Evinrude 7.5 Fleetwin this past winter (new plugs, wires, coils, impeller, head gasket, cleaned the cylinders, rebuilt carb, cleaned and lubed all throttle linkages, added a vaccum-driven fuel pump and all new lines, new, modern fuel tank and fuel line/bulb assembly), and have been trying to get it to run well in a bucket in the driveway.

Right now, it will start after a 2-3 pulls but it will idle rather roughly. If I increase the throttle to 3/4->WOT it will run faster, but after about 2-3 mins it will surge and if I adjust the throttle, it stalls out 9 times out of 10. Only once was I able to pull it out of the post-surge stall, and it ran super smoothly after that... weird. Plus, every time it surges the bulb goes soft, and it won't start again unless I manually repressurize the fuel lines. While doing this, I can hear fuel getting dumped into the float bowl of the carb when I squeeze the bulb. The bulb gets hard again once the carb is full, and I have inspected for leaks multiple times, so I don't think this is an issue of fuel leaking from any of the lines.

So any thoughts??? From what I've read from the experts here, and elsewhere, there are a few options…
1. Something is wrong with the carb?
2. One of the cylinders isn't firing?
3. Something is wrong with the tank or fuel lines that starves (or floods?) the engine?
4. Maybe it doesn't like idling at high speed in the bucket... should I take it out and put it under load?

I'm really scratching my head here... Any help would be greatly appreciated. Thanks!!!
 
Get a ohm meter and remove spark plug WIRE and check
the ohms for each wire. It probably should be around
ZERO. Hold the probs to the wire while moving the wire
around making sure the reading is STEADY. If it fluctuates
replace the wires.
 
bigjohnson said:
Get a ohm meter and remove spark plug WIRE and check the ohms for each wire. It probably should be around ZERO. Hold the probs to the wire while moving the wire around making sure the reading is STEADY. If it fluctuates replace the wires.
Click to expand...
Thanks. I can check, but the plug wires are new.
 
I also swapped out the 3-prong fuel plug in on the tiller arm bracket with a used 2 prong plug, so it is compatible with 2-prong modern tanks and fuel lines. No more positive pressure! Sorry - should have mentioned that!
 
Ok, I've got an update. I checked the spark and both cylinders were putting out a strong spark at about 1/4 of an inch gap. So I figured I was dealing with a carb issue at that point. Although I've tried to fool with the low speed and high speed controls, starting at recommended settings (1 turn for low speed, 1 1/2 for high speed), I couldn't get it to run smoothly in the bucket, especially after it was breathing fumes for a while. So based on a post I saw somewhere here, I turned the adjusters down to zero (just seated), and fired it right up. It ran nice and smoothly, accelerated smoothly and didn't smoke hardly at all. No gagging or stalling either! So the next step is to put it under load on the lake and do the carb adjustments.

Also, is there a good supplier for these carbs or major replacement parts, like the needle valves? Ebay is all I've found so far.
 
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