Severe lean sneeze?

[oldcatamount]

I have a 1964 Evinrude 9.5hp. I can start this motor with one pull of the cord (almost) every time. However, it will run great for about a minute and then start stumbling. It sounds like a lean sneeze but, it is so bad, it almost stalls the motor. I have taken the carb off and cleaned it thoroughly several times, replaced the fuel lines and after I discovered the gasket underneath the fuel setiment bowl was missing, replaced that with an o-ring. I changed the fuel pump (with another one I had in the shop) and it made no difference. While it's running (and stumbling) I squeeze the fuel primer bulb and it makes no difference. While it's running, I have turned the low speed needle outward (in 1/8th increments) until it's out more than 3 full turns and it makes no difference. The motor doesn't respond to the needle valve unless I turn it all the way back in (and that will kill it). The ignition seems ok. It has a nice sharp, blue spark on the tester (both cylinders). I set the timing (with my brand new timing fixture) and it's right on the money. The compression is at 85 pounds on both cylinders (cold). This "lean sneeze" is quite severe or so it seems to me. When it happens, the motor will almost die, take several revolutions to recover, run good for a few seconds and it'll do the same thing again. It has the same sneeze at low speed and at high speed. I need help on this motor and any suggestions will be tried and appreciated.

 

[kbait]

Re: Severe lean sneeze?

Are you sure you got the low speed circuit all clean? At 3 turns out it should be way too rich to idle. Did you pull the welch plug that hides the low speed ports to the carb throat to clean those holes? Sounds like the low speed circuit is still gunked up, or you have a vacuum leak at the carb base gasket. Could possibly be a leaf valve under the carb not seating.. starving one cylinder. I'd run it with one plug wire pulled (and grounded) and then the other to see if it's only sneezing on one of the cylinders. If it is, I'd look at the reed valve for that cylinder. If it sneezes on both, low speed circuit/carb gasket. Good luck!

 

[OptsyEagle]

Re: Severe lean sneeze?

The other thing to do is try to re-choke it when it starts to sneeze. This should help to recover it a little. If it doesn't, then perhaps it is not a lean squeeze.

 

[kbait]

Re: Severe lean sneeze?

You said it has the sneeze at high speed too.. do you mean in the barrel, or wide open on the lake? In a barrel, it's probably still running on the low speed circuit to medium throttle. If it's sneezing wide open on the lake, that takes the low speed circuit out of the equation, since it should run wide open well even if the low speed jet is cranked in (disabling it). I'd still try the test above, and check for a leaky carb mounting gasket by spraying some carb cleaner around the base of the carb while it's running (on both cylinders) to see if the sneeze goes away. If it does, you have a vacuum leak. Post back w/results..

 

[kfa4303]

Re: Severe lean sneeze?

these may help:


http://www.outboard-boat-motor-repa...hnson 5.5 HP 1954-1964 Carburetor Tune-UP.htm

http://forums.iboats.com/showthread.php?t=167352

http://www.iboats.com/Carburetor-Ki...15.1964--**********.717183560--view_id.174131

 

[oldcatamount]

Re: Severe lean sneeze?

When I cleaned he carb (for the fourth time) I took out the welch plug and cleaned the chamber (and orifices) and blew compressed air through them. I then replaced the gaskets under the carb and under the intake manifold. The reeds appear to be ok. All are seating good and no apparent signs of cracks or chips etc. I'm running this motor in a barrel (without the cowling). It'll sneeze at idle and it'll sneeze up to 1k rpm (app.) That's about as fast as I can run it in the barrel (without blowing the water out). I'll try looking for a vacuum leak with the carb cleaner spray. Thanks for all of your help, I'll post back hopefully with some good news!

 

[kbait]

Re: Severe lean sneeze?

I wonder if it could be leaking air in from the upper or lower crankshaft seal? I've never run across that myself, but heard it happens. I'm sure you replaced the low speed needle packing as air leaking through there would cause this issue. Be sure to perform the carb cleaner spray test.. maybe there's a crack in the carb body? kinda grasping for anything here..

 

[oldcatamount]

Re: Severe lean sneeze?

I did replace the lower crank seal (what a pain in the ars that was) but, I did not replace the low speed needle packing! I was just looking at the carb casting for cracks but it seems to be fine. I just took out the reed assembly and they look good as well. I'm going to flip the reeds over when I re-install them and I have to make my own gasket for the reed housing. Looking down inside the crank case everything looks like virgin territory in there. Nobody else has been wrenching on this motor at all (as far as I can tell).

 

[1946Zephyr]

Re: Severe lean sneeze?

Check the ignition system. Make sure your points are clean and gapped properly. Also check the condition of your coils. A lot of time ignition problems will make us think it's carburetion.

 

[ultra353]

Re: Severe lean sneeze?

I had the same problem with the low speed sneeze, tried everything, replaced everything on my `68 9.5. I got a different carb and needle off ebay, runs great now! Turns out my slowspeed needle tip had been broken off and someone before me filled it down. Compared to the correct needle the old one was more blunt ( hard to tell if i didn`t have a good one to look at). It would never meter the fuel right.

 

[oldcatamount]

Re: Severe lean sneeze?

Ultra...I just took a look at the tip of the needle valve and it appears fine. I even used a magnifying glass for an extra close look. I'm thinking it may be an ignition issue also but, the spark is bright blue and even as deaf as I am, I can here it snap! I'm going to try the carb cleaner around the carb base in the morning (daylight).

 

[HighTrim]

Re: Severe lean sneeze?

I would follow Kbaits original advice and run it on one cylinder at a time to see if it is only sneezing on a particular cylinder. That will narrow the likely problems down a little.

 

[1946Zephyr]

Re: Severe lean sneeze?

Believe it or not, I had bad coils deliver good spark, but wouldn't fire a cylinder. Try what HighTrim suggests and that will narrow it down.

 

[F_R]

Re: Severe lean sneeze?

Are you sure the carb/spark synchronization is correct? A carb throttle that opens to soon (or doesn't close at all) will do that.

EDIT: Ah yes, the 1964 model!! How about the vibration damper and mounts? Especially the vibration damper. Those dad-gum things shook so dad-gum badly that they wouldn't idle. Try a temporary fix by somehow holding the powerhead still and see what happens.

But still----check that syncronization.

 

[oldcatamount]

Re: Severe lean sneeze?

SUCCESS! Although I'm a bit embarrassed to admit it, it seems that I had misdiagnosed an ignition problem for a fuel problem, but the motor runs like a wrist watch as we speak! I installed new points, condensers, and plugs this morning and it cured the sneeze. Although the old points looked good to me. I adjusted the carb/spark synch (just a touch), installed a new packing on the needle valve, and re-installed the vibration damper (that I had forgotten to do the previous time I had the carb off), and now this motor runs better than ever! The only trouble is that I've already wintered my boat so I can't take it out and lay the whip to it until spring! You guys are a big help to me, I really appreciate all of your suggestions and advice! Thanks a Million!