'62 10hp Evinrude

[oldboat1]

figured I could get this one up and running for use next month, but now not so sure. Is there a rule-of-thumb response for backfiring at the carburetor (rather than the exhaust)? Coils and points look fine; points adjusted to .020. The key was in place (not sheared off). I cleaned the carb -- still had the backfiring, and can't dial it in (won't idle down, which was the complaint by the former owner). I've replaced the t.stat which was stuck open -- motor was running cold.<br /><br />This afternoon, I replaced the fuel lines and clamps, and also put in a fresh set of J6C plugs -- haven't tried to fire it up yet with those fixes.<br /><br />Any troubleshooting ideas on backfiring through the carb?

 

[JB]

Re: '62 10hp Evinrude

Did you check the reeds, oldboat?<br /><br />I am not sure I understand what you mean by backfiring at the carb. Is that what we usually call sneezing, or is it a bang?<br /><br />Sneezing is a sign of too lean mixture. If it happens at idle it is likely that the cleaning missed a blind passage in the idle circuit.<br /><br />Good luck. <br /><br />Does the engine run at all?

 

[Joe Reeves]

Re: '62 10hp Evinrude

If by backfiring, you're speaking of a mild type sort of backfire, actually a spitting back thru the carburetor type thing, that's due to a lean setting of the carburetor.<br /><br />That sounds like you may have possibly overlooked something within the carburetor (easily done). I'd suggest that you remove the carburetor and double check it.<br /><br />(Carburetor Adjustments - Two Adjustable N/Vs) <br />(J. Reeves)<br /><br />Initial settings are: Bottom high speed = seat gently, then open 1 turn out. Top slow speed = seat gently, then open 1-1/2 turns. <br /><br />Setting the high and low needle valves properly:<br /><br />NOTE: For engines that DO NOT have a shift selection, obviously there is no NEUTRAL position. Simply lower the rpms to the lowest setting to obtain the low speed needle va /lve adjustment.<br /><br />(High Speed) Start engine (it will run pretty rough), shift into forward gear, take up to full throttle. In segments of 1/8 turn, wating for the engine to respond between turns, start turning in the bottom high speed needle valve. You'll reach a point whereas the engine will either start to die out or spit back (sounds like a mild backfire). At that point, back out the needle valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest setting. <br /><br />(Low Speed) Slow the engine down to where it just stays running. Shift into neutral. Again in segments of 1/8 turns, start to turn the top needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running. Eventually you'll hit the point where the engine wants to die out or it will spit back. Again, at that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting. <br /><br />When you have finished the above adjustments, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.

 

[oldboat1]

Re: '62 10hp Evinrude

Thanks, JB. This is backfiring, not coughing (and at the carb). Which is to say, a puff of smoke with the pop -- model has a flame arrestor, but would almost expect to see a flame. I've never repaired reed valves, although I was thinking that may be the next step if I need to pull the carb off again. I didn't fully open up the idle passage, but can run a wire through the orifice. I can get the engine running at mid-range speed, but it finally backfires and will stall -- won't restart, and (sheepishly) I have been resorting to starting fluid.<br /><br />I'm going to repack at least the high speed needle as I think I'm getting a little leakage there. The float seemed OK, and properly adjusted. I just don't know whether this is likely to be carburetion or electical. It's not like an exhaust backfire, which (on other motors) I've usually been able to correct with a richer idle mix. I can't seem to get this one down to the point where the idle mix is a factor.

 

[oldboat1]

Re: '62 10hp Evinrude

Joe -- used your method many times with success. Thanks. But on this one, I'm not sure.<br /><br />I gather that backfiring (including spitting or coughing) from the carb isn't really any different from through the exhaust as far as troubleshooting is concerned. I'll add a couple of the old-style cork packing rings to the needles, and then set them both again. Maybe with the new fuel lines I corrected an air leak. If I still can't dial it in, I'll probably pull the carb and go through it again.