If this feels like 4/4 time with an extra beat tagged on at the end, then I would count each measure as:
If you want the pattern to count up and don't need to worry about accenting a particular beat, I would recommend this:
Then, internalize the "ee-and-uh"s so that you don't have to count them out loud. This leaves you with:
1 / / / IS / / / SEV / / / EN / / / TEEN`
2 / / / IS / / / SEV / / / EN / / / TEEN`
3 / / / IS / / / SEV / / / EN / / / TEEN`
If you were to learn this method, it would be easier because you'll only have to count 5 beats, and the rest you will be able to simply feel intuitively.
Another value of this pattern is that, if you are learning to count/feel lots of different odd meters, then you can easily remember which one is 17/8 versus, e.g., 15/8.
If you want the 17 beats in groupings of 3 (so that every third beat is a strong beat), then you could use:
Once you internalize the weak beats (the "and-uh"s), you can count it more easily like this:
1 / / THIS / / IS / / SEV / / EN / / TEEN OH
2 / / THIS / / IS / / SEV / / EN / / TEEN OH
3 / / THIS / / IS / / SEV / / EN / / TEEN OH