Hi Othello,
Like Nuno said, you need to hack the heater. Here is a useful link how to hack it. The goal is to spread the bi-metal a bit wider. With a screwdriver, thermometer and some experimenting you will do the job fine. I've also hacked my heater which can reach 60 degrees Celsius. The important thing is to be very careful when you're pulling out the rubber sealing/top. The glass can be easily broken. Regards.
http://pcbheaven.com/exppages/Removing_the_built-in_thermostat_of_an_aquarium_heater/