The size of the flue and the positioning of the spiral baffle are CRITICAL to proper operation on LP. If the baffle is even a little off on ID or length and the baffle is not exactly positioned as the original, that could be the cause of your problems.
Also, your burner nozzle may be clogged and should be cleaned. Don't put anything thru it! Just soak in carb cleaner and blow it out with air. That might solve your flame problem. You should also check the pressure at the gas valve (11" water guage) and blow out the line from the valve to the burner. It might be fuel starved due to a blockage, or bad gas valve pressure.
Lew Farber...RVIA Certified Master Tech...ABYC Certified Master Marine Electrician
SOLAR TECH ENERGY SYSTEMS, INC.
AM SOLAR ...MAGNUM…VICTRON ENERGY...LITHIUM & LIFELINE BATTERIES…MARINE REFRIGERATION