Im overweight and just started walking. im 34 and weigh 285. my heart rate was 126bpm after 1.5 mile walk on contry roads is this a good heart rate?

It's fine: It would be expected if you're starting an exercise regimen that your heart rate may increase easily, especially if you've been sedentary for some time. You should feel a bit tired, winded, sweaty, etc at the end. It shouldn't be so easy that you can have a full conversation the whole time. Bottom line: don't worry about the heart rate; feel good about this positive change you're making.

Appropriate HR: Yes, this is an appropriate heart rate response for your age. To calculate your your age appropriate heart rate maximum, the formula is 220-age. (For you that would be 186bpm).However, to exercise effectively for weight loss the formula changes to 0.85 x (220-age) (For you: 158 bpm. Maintaining your heart rates below 158 bpm during your daily exercise will help you lose weight and exercise longer.