Re: Mercury 50 HP - 2 stroke: will not start, alarm sounds.
I don't have a manual on a 50 hp. On the higher hp engines it monitors oil in the oil tank for the oil injection system and temperature.
On engines without a modulating chip, either could give you a solid alarm. Common problems reported on here are the magnet that is used to ensure that there is adequate oil in the tank falls off and when it does the alarm goes off.
The over temp is a temp switch that closes around 195F which is well above the tstat opening temp. If you touch the key and it sounds and the OT sensor is causing it, the switch is shorted.
On my engine 2 lt. blue wires come from the tank for this purpose. The over temp is a tan or tan with lt. blue stripe.
You can disconnect these wires between the sensors and the engine to control box wiring harness connector and see if it goes away. If so reconnect individually and see which one it is. If not look for a short in the tan/blue stripe wire going to the remote control on pin 3.
Now, the will not start part of your thread bothers me. The black/yellow stripe on pin 1 of the same connector is grounded through the ignition switch in the OFF position. Otherwise it floats...voltage determined by ignition modules. This keeps the ignition modules from producing spark and is used to kill the engine.
You said you kept your engine tilted up. Do you have a binding harness, or rats or mice that could have chewed insulation exposing a grounded cable shield to these wires? Would be the right answer to solve these problems.
Mark
