Unexplained stalling in Engine timing

[Mfoxchicago]

Good evening Captains:
While on our regular run today, all systems were fine and TULE was chugging along well. Then we stalled out, for no apparent reason. My Chief tapped on the manual timing lever and she got back in to rhythm. We completed the run and returned to dock. On our second run, approx an hour later, we headed out fine, about half way through a 50 min. run, she stalled out again - Chief tapped the timing bar she came on, ran another fine for another 6-10 strokes and then stalled out again. Same fix. We finished our run, returning to the dock on schedule. The very next run, with 4 passengers aboard, we left the dock, traveled about 100 yards and she began stalling out repeatedly, with only the engineer's continual manual tapping of the timing bar to keep getting her back in to proper timing. We returned to dock, disembarked our passengers safely. We chose to do another run, close in range to our dock, without any passengers, with Captain & Chief listening and looking very, very closely at the engine and her timing linkages for any malfunctions or apparent causes for the stalling. Nothing. She ran without incident - for 15 minutes. We returned to dock and bedded her down for the night.

I am at a loss for reasons or explanation. I am hoping more experienced minds will have some idea of what I may be facing and how I might go about ascertaining the true nature of this anomaly. My Chief & Fireman joked that "she just didn't want to do any more work today". I know there will be a very realistic and plausible reason for this issue and a fix. I am standing the boat down tomorrow due to high winds and possibility of rain - but I do need to know if this is a minor annoyance that can be rectified or am I facing a major repair nightmare that will prematurely end my first season with 4 weeks to go.

I value and anxiously await your advice guys. Thanks.

[Kelly Anderson]

What kind of valve gear does she have? Any photos? Does she exhaust into a vacuum? Did you loose the vacuum just prior to stalling?

[Mfoxchicago]

Thanks for replying Kelly. TULE is an authentic walking beam engine. You can see our website at http://www.tuleprincess.com Check out the pictures section on the engine.

She has (2) poppet valves at the top and bottom of the main cylinder. She does exhaust to a vacuum, through a keel condenser and then back to a hotwell. My Chief has reported we were running a consistent 7" of vacuum on the vacuum pump. Don't think he was looking at the vacuum gauge when the stalling occurred. I suspect his first point of view would have been the the timing linkage and getting the regular rhythm going again.

[Kelly Anderson]

I was unable to find any good photos of the engine on your web site.

Usually a valve gear malfunction doesn't go away on its own, the engine stops and stays stopped until repaired. With poppet valves, there is a possibility that one of the valves is sticking open, then snapping shut when the engineer manually restarts the engine. Loss of vacuum could cause a stall due to loss of power, but with only 7" (if that is her normal amount (25" is desired)), you are not gaining that much power from the vacuum anyway.