I have a 6-8 year old Hayward H150 pool heater. The pilot light will light but the heater won't kick in. I can't afford a new one . What should I do?

If you have voltage to Heater and it is not heating, it is likely bad.
New Heaters are about $200.

New heaters are around $1250 for an above ground pool. This is a natural gas pool heater for a 24 foot by 52 inch pool

Could be a few things, loose wire connection (not getting the correct MV), pressure switch, gas valve (not pilot generator, if it is staying lite) roll out safety switch bad, bad thermostat.

They are fixable, pending on your knowegle, it may be dangerous to go trying to many things on your own. Need tester to test gas valve output.

If you have a sand filter, turn to recirculate and then see if the heater comes on. May be a restriction in water flow through the filter.

Shows how to replace/adjust pressure switch, and pilot generator wires that may have bad connection.
http://www.haywardnet.com/products/M.../Manual285.pdf