Hayward H200 heater pilot will light but unit doesn't get very warm

I have a Hayward H200, installed used 3 yrs. ago, at the time was 3 yrs. old. Can light the pilot but when turning up thermostat, the heater does not get as hot as in the past. Any ideas, or places I can look online for repair manual, etc. I live near chicago and all the pool companies are so busy they're not taking new customers currently aaaargh!

How can I put this delicately? I can't, so here it is: servicing millivolt pool heaters stinks!

Here's your manual: http://www.hayward-pool.com/pdf/manuals/Manual285.pdf

And here are two posts on the problems:
http://www.poolforum.com/pf2/showthread.php?4839
http://www.poolforum.com/pf2/showthread.php?12250

Good luck!