BF50 runs fine then won't ...

I have a 2001 BF50 tiller that runs great for about 40 minutes. After being off but still warm, it will start but as soon as shifted into gear dies. I have changed oil and filter, put in new factory water pump kit, changed gear case lube, put in new fuel pump, fuel filter, thermostat, and fuel line/filter/ bulb. Here are my questions: Does the engine have a disable feature from overheating and or oil pressure and would that feature allow it to start but then die when shifted? If I disconnect the yellow and orange wires (from the senders), would that eliminate the disabling inputs? Having read many posts in here, today I will take the lower unit off and try to flush with garden hose. The water from the pee hole is never that hot. However, the impeller I removed was really in bad shape, so there may be pieces in the engine. Compression was 195, 190 and 185 cold and dry. They all hit 195 with a squirt of oil. Plugs are relatively new and look fine.
Any other driveway tests I can do? Thanx in advance for your time and inputs.

Additional info....there are no indicator lights on this engine ...I bought it used. Blew out the water tube and only 1 tiny particle (coarse pepper size) came out.. 9 inches up the pipe there is some sort of seal? I pushed a wire in and scraped around the inside of the tube but the wire can't get thru this seal, at least with light finger pressure.
How does the disable function actually work....I presume its electrical. I will go buy an infrared heat sensor to check the head temps.