I tell strangers I love them but they take it the wrong way like as in marriage love when I don't care for that stuff. I'm only 17. What should I do about this ? I tried to ignore them but that didn't work.

Instead of using the word love, replace it with another word like admire, adore, cherish, fancy, fond of, or treasure .

You may have Christian love for your fellow mankind, but saying so to complete strangers will have people looking at you like you have lost your mind.

Exhibit the love that you have for everyone by being kind, being helpful when you can, doing random acts of kindness without telling. Feel it in your heart but keep the words for someone very special. It holds no meaning if you are constantly telling everyone around you that you love them. Make it mean something.

Stop telling strangers that

Get out of the habit of saying nice things to strangers, it always sounds phoney. Above all, NEVER tell a stranger that you love them; that is most definitely off-putting and practically guaranteed to make them avoid you.

Tell your family and friends you love them. Give compliments to strangers and keep walking. I do everyday. 

I think when you say it in a Christian way it shows you do not know Christianity at all. I mean you do not know religions at all. Religion (any religion) does not provide love, all it gives is hatred and grudge. You are still way too young and you will see what I say when you read more about religion. So my advice would be: Do not do it. There is no such thing as Christian love. Replace the words with actions and show people how much you love them. Words can be misleading.

Why on earth are you telling strangers you love them?! Is it really any wonder they think you're weird?

In one of your comments you say that you love them in a Christian way and you don't know why they don't understand that is what you mean.

Here's three definitions of "love" from the internet:

(1):  Strong affection for another arising out of kinship or personal ties <maternal love for a child>

(2):  Attraction based on sexual desire :  Affection and tenderness felt by lovers (and)

3): Unselfish loyal and benevolent concern for the good of another

When people hear the word love without a specific context, the second definition is what people are conditioned to think about first.

So what you mean when you say you "love" a stranger, #3 is just not the first thing a stranger thinks you are saying---which makes them think you are weird.

Communication requires a sender and a receiver.  The message you are sending is ambiguous (because of our culture) and the receiver doesn't associate with what you actually intend to communicate.

Those are the facts.  You can decide what to do from there.

As you said these people are strangers. They do not know you mean it in a Christian sense. And many people are not Christians and do not want your religion thrust upon them. Instead of saying you love them, (which franly will come off as insincere if said too often) show them. Show them kindness and respect. If you know it bothers people, yet continue to do so, you are not showing any kind of love, kindenss, or respect. You are ignoring their feelings all together.