It is import for your safety and enjoyment of powered paragliding to choose a motor that has the right amount of power. Your weight is the primary determining factor, but there are other considerations including the altitude of your launch site and your physical abilities.
Buy the lightest paramotor you can afford
Many pilots start out with heavy powerful paramotors. There are plenty of used ones for sale because these pilots eventually realize that light is king, unless you launch on wheels. For foot launching, the lighter the paramotor, the easier it will be to stand up, launch, and everything else you have to do with a paramotor on the ground. Be warned! Manufacturers lie about empty weight. Don't trust numbers on the web. Go to a dealer a put one on your back. You may be very sorry if you don't do this.
Not enough power?
If your motor has insufficient power, your takeoff run will be longer, increasing your chances of tripping and falling. You’ll also need a bigger launch site. And if you do get airborne, you may not have adequate climb power to safely avoid obstacles. However, not enough power is hardly ever the problem.
Too much power?
Although more thrust can make launching easier, powerful motors are heavier, making ground handling more challenging. Bigger motors also use more fuel so your cross country range will be less, and the amount of fuel you'll need will increase, which further increases ground handling loads. If you launch on wheels, weight is not an issue.
Weight Ranges are only a starting point
Manufacturers reccommended weight ranges are usually not accurate. Altitude and physical ability play a role and must be considered. Before making your final decision, talk with instructors and pilots to get a feel for what experienced pilots are actually using. The distributors and manufacturers want to sell you their gear. Seek out instructors who sell more than one line of equipment and reward them by purchasing from them!
The horse power quotes from manufacturers are not alway accurate. Also look at displacement but that doesn't always tell you the whole story. For example, the Solo 210 was a great engine years ago, but now this old 210 cc design has about the same amount of power as newer 100 cc motors than weigh far less.
Bigger propellors have more power. Get a big prop!!!
Get a paramotor with the biggest propellor possible. The taller you are, the bigger prop you can have. The bigger the prop, the greater the power and efficiency. A smaller motor with a bigger prop can be more powerful than a big motor with a small prop. Of course the paramotor cage needs to be large enough for the bigger prop. Most pilots 5 foot 9 inches or taller can fly a 51 inch (130 cm) prop. The trade off is that bigger props can reduce clearances from the ground and cage on some paramotors. If you are concerned about prop clearance, you can start with a 48 inch prop and add a 51 inch after your skill level increases.
The higher the altitude, the thinner the air and the more power you need. If you live at higher elevations, you may need to step up to a bigger motor. However, in some cases, a slightly bigger wing can make up the difference. Every situation is different. Only an experienced instructor is qualified to zero in on the best choice for you.