S115 99 2-stroke drops power at 5000 rpm

[cliff mock]

The S115, idles and runs well up to about 3800-4000 rpms. When you get above 4500-WOT within a couple of minutes the alarm goes off, and you lose power to the point it comes down off of plane and you can hear the prop back drag. The heat guage and oil guage show no alarm. The water from the discharge hole is cool. Can sit at netural idle for a minute and the alarm goes off, as well as switch off and turn back on and the alarm is off. Check the oil in the oil tank on the engine and it is fine.
When you come down off of plane and the alarm is still on, and try to get back on plane, the engine just shutters, but wait until the alarm goes off and it hops right back up and runs fine until you exceeds 45-WOT.
Always change thermostats every year, fuel filter, and plugs. Even replaced fuel line. So I have done all the dum things. What is you best guess? How to trouble shoot?

[Moonman62]

Carbeurators

The S115, idles and runs well up to about 3800-4000 rpms. When you get above 4500-WOT within a couple of minutes the alarm goes off, and you lose power to the point it comes down off of plane and you can hear the prop back drag. The heat guage and oil guage show no alarm. The water from the discharge hole is cool. Can sit at netural idle for a minute and the alarm goes off, as well as switch off and turn back on and the alarm is off. Check the oil in the oil tank on the engine and it is fine.
When you come down off of plane and the alarm is still on, and try to get back on plane, the engine just shutters, but wait until the alarm goes off and it hops right back up and runs fine until you exceeds 45-WOT.
Always change thermostats every year, fuel filter, and plugs. Even replaced fuel line. So I have done all the dum things. What is you best guess? How to trouble shoot?

No Etoh gas,Rebuild carbs, keep your water seperator current,. forget the thermostat. Just a little something to try.

Good Luck, Moonman62

[rodbolt17]

DO NOT ditch the T-stats.

thay are part of the water pressure control system

what guages do you have for visual indicates?

not all have an icon for overheat just low oil.
your describing a classic hot spot due to scale buildup.
typically found on saltwater engines.

its gotta be one of two.
low engine tank level or one of the temp switchs.
low engine tank will indicate on the 6y5 tach.
overheat may or may not depending on the tach and the rigging.
a quick test?

when it does it pop the hood and unplug the temp switchs one at a time and see which one shuts off the alarm.
an infared temp gun is handy as well.
in a typical hotspot alarm the engine will cool off sufficiently to shut off the alarm in a minute or two.
an actual engine overtemp usually takes 10 to 15 min to cool back down.