Stalls Under Load

[Bakerd]

Engine starts and runs well at idle. Sounds strong and smooth. Temp is OK @ about 180-185. When we engage the prop, it will run for a period of time (5-10 mins) and then you can hear the RPM's beginning to drop and will then stall. The stall can be prevented by taking it out of gear back to idle. It will idle fine. Back into gear it will run for a while (2-3 mins) then again PRM's drop to stall. Temp is still ok. Also the more throttle applied, the quicker the stall will occur.

One other thing is I think the alternator is bad. Having battery trouble as well. Batteries are good. Took to Autozone and "Charged". Held charge and checked out ok. But over a fairly short period batteries are not charged. Will have Alt rebuilt. Can this be a part of 1st issue? or are they most likely separate issues.

Thanks

[Kelly]

This is not my field of expertise (I don't have one, actually) but your symptoms sound like classic fuel starvation.

Things to check for clogging: gasoline tank vent, fuel lines, primary fuel filter, secondary fuel filter (if you have one).

Check the fuel pump (electric?) by running the exiting fuel line into a jar. See if you have good flow.

If you still have problems, does the carb need cleaning?

Kelly

[Don Moyer]

A faulty alternator can indeed result in the batteries becoming so low that the inductive process within the coil (actually the secondary discharge) will become weak enough to result in a power loss. Unfortunately, I can't give you a system voltage where this secondary discharge reduction occurs since we have never done any testing in that regard.

When I was young and "generator" problems and weak 6 volt DC systems were much more common than is the case in alternator charged 12 volt systems of today, I recall that when a generator failed you could feel your engine lose power when the head lights still provided enough light to see where you were driving - though barely. I'm guessing rather wildly that most coils in our 12 volt systems would show a decreasing secondary discharge below 7 to 9 volts (as measured at the positive terminal of the coil).

Don