Engine stalling

[Bob N]

Don, I have a problem with my engine stalling. After the engine is well-warmed up--like when I am motoring back to my slip after a few hours of sailing, it will stall as I throttle it back to idle making the approach to my slip. Needless to say, that creates a rather exciting moment at just the time when I want to give a burst of acceleration in reverse to stop the boat. (I go into my slip bow first.)

The first time this happened was after the boat had sat idle for a couple of weeks. After stalling, it would not restart. When I pulled a sparkplug, I could not smell gas in the cylinder and the plug was dry. When I used a jumper wire across the oil safety switch, it started right up. Cleaning the contacts on my oil safety switch (not the one you sell Don, but one that you press the wire connecters onto prongs on the side of the switch) solved the problem. My theory is that corrosion on the contacts shut off the fuel pump caused the sitch to cut out at 20-25 lbs--instead of 10-15 lbs--as the engine was throttled back. I've noticed that when the engine is fully warmed up, the pressure drops to 25lbs or so when I throttle back to idle. My oil pressure at idle when cold is much higher, of course, so the engine idles fine when cold.

The same problem happened again last weekend, but, fortunately, the engine refired immediately. I haven't yet been back to boat, but I will clean the switch contacts again. But do you think it might be a blockage in the carb? I also saw in one post that you suggested that boosting the idle adjustment might help a similar problem. But the engine has been has been running fine for a couple of seasons. I am considering replacing the cheapo oil safety switch with one of yours, but I don't want to chase after the wrong solution. Do you have any suggestions, Don?

[Don Moyer]

Bob,

Your work with the oil safety switch sounds quite convincing, at least circumstantially, but I'm not sure that you're not being misled. When an engine stalls out at idle (after being fully warmed up) it's frequently the case that the float valve is allowing too much fuel into the float chamber. This condition tends to flood the carburetor at idle and causes the engine to stall.

The next time you experience this condition (which you should attempt to plan for a less stressful time than docking) try to retard the throttle slowly so that you can determine if the engine is running very rich just as it is trying to fail.

You might also try to hot wire around the safety switch to see if the problem goes away. If it doesn't, I'd pursue the float valve issue.

Don

[Bob N]

Could it also be the idle mixture?

Thanks, Don. I will experiment with the jumper wire when I go out have it well-warmed up--out in open water and not on "final approach" into the slip. Looking at another post, I'm wondering if boosting the idle might also help, although, as I say, it has run fine for quite a while before this problem cropped up in August. By the way, what led me back to the oil safety switch was that cleaning the contacts worked the first time this happened. The problem came back after the boat sat idle for 3 weekends--including some rainy, humid weather--as had been the case the first time.

But it looks like my winter project may be taking apart the carb. It was probably due for a cleaning, anyway. (I try to follow Dick O'Kane's advice from Road & Track many years ago: "Carburetor is a French word meaning 'leave it alone,'" but I know you encourage us to me more proactive in maintaining our engines.)

[Bob N]

Success?

I cleaned off the contacts once again and the problem seems to have disappeared. I couldn't reproduce the failure when the engine was warmed up, and had no problems docking. I will buy one of you oil safety switches (a local mechanic installed the one I have now when I bought the boat 6 years ago), since the srew terminal contacts look much more substantial.

Thanks for your help, Don.