1954 Evinrude 75 HP Idling issues

"I recently aquired a 1954 Fle

"I recently aquired a 1954 Fleetwin model 7516 that ran but not well. At high speed it ran really rough and at idle I had to fiddle with the low speed screw constantly to keep it running. I cleaned the carb, replaced the float, gaskets, needle and seat, and both needles(both badly grooved). Now it runs great at high speed but is still rough at idle. It will idle for extended periods without touching idle screw now but is rough. Tried leaner, and richer but this is the best it gets. Any suggestions?"

"did you clean ALL the orifice

"did you clean ALL the orifices in the carb manually or did you just spray them with carb cleaner and/or compressed air?

how many adjustment screw do you have?........ sorry im not familiar with your eng, but i do have a carb adjustment from a guru by the name of joe reeves http://forums.iboats.com/showthread.php?t=167352"

"Those adjusters had a packing

"Those adjusters had a packing seal and cinch nut. Sometimes the threads the needle went in (a seperate piece)would spin in the carb giving the impression of adjustment. You might check that.

The adjustment of one needle changes the fuel to the other. So you had to get a relay going till both adjustments worked. Then set the pointers for the knobs to the center so you knew where it runs the best.

Your ignition has a lot to do with how that engine runs at idle. Might hook up a timing light and see if it is dropping out.- Not sure when, but some had a set of "tower" points and reverse coils which fired off a magnet shaped like a hockey puck on the crank shaft, not cast to the flywheel. These points were run off a fiberglass rod that would get sticky with out service.-just a thought.

That motor has a spring loaded carbon seal for a lower crank seal. They would get damaged when changing out the water pumps --so next time you have the lower off, shine a light up there and see if your lower seal is OK. They really ran ratty with out it."

"I dissasembled the carb then

"I dissasembled the carb then soaked the metal parts in Gunk carb cleaner for about an hour, rinsed with water then blew out all the passages with compressed air. The one thing I did notice was that the valve packing was a bit ratty, but seemed to be functional. I couldn't find new packing.
I had the lower off at the same time to replace the water pump impeller, I assume the seal you are referring to is the carbon one with an o-ring in the top? It looked ok but perhaps not. Also could the power head to lower unit gasket cause any problems? I did not replace that either."

"One more note. I have slow s

"One more note. I have slow speed and high speed scews, adjusting them does change the way the engine runs and I have them where high speed is clean but can't get idle to run smooth. I can lean it out till it pops and richen it till it dies but can't get it smooth on the low speed circuit.."

Compression test?? Ignition sy

Compression test?? Ignition system??? Point gap?? Coil and plug wire condition??? Fuel to oil ratio??

I have a 1955 5.5hp Johnson th

I have a 1955 5.5hp Johnson that had badly cracked coil insulation. Not sure if they're the same style coils as yours but it never ran right at low speed until I replaced them with new ones. Runs great now.

"compression good, point gap g

"compression good, point gap good, plug wires look ok externally, fresh fuel 24:1 ratio.
I will take a look at the coils and wires under the flywheel, could be the issue.
Thanks"

"While you have the flywheel o

"While you have the flywheel off, check the upper crankshaft seal. If the motor is sucking air it wont idle worth a darn. Drizzle a little oil on that seal... spin the crankshaft the best you can and see if it bubbles or disappears into the motor, if it does, suspect the seal being bad. Worth the time if you have the flywheel off anyway."

Sounds like a good idea thanks

Sounds like a good idea thanks