Its average density will have to go up by 50% also. If the planet is made from a different balance of elements (iron, silicon, others) than before or the Earth, that will give it a much larger iron core. Then the cooling time for that core will be lengthened by a large factor.
The Earth has a much larger iron core, by proportional content, compared to the elements contained in the nebula that surrounded around the sun. That larger iron core exists where it should not. It is a product of two smaller early planets colliding and merging. So its core has remained partly fluid for billions of years due partly to that larger size. Other factors are radioactive decay heating and stresses caused by the orbiting moon.
In the case of Mars, while an increased mass would mean a larger core like Earth has, the ability of its core to remain partly fluid might not be as long as in the case of Earth. No large moon to cause mechanical friction heating. And not sure about radioactive decay heating, but it might not be as great either.