After running the AC on my IP 29 for several days the volume of air flow from the vents has dropped considerably and the boat is not cooling. The seawater water circulation has not changed and is good.There is frost on the coils of the unit. Don't know if this is a problem. Any ideas on what is causing these issues?
Turn compressor off and turn fan to on to defrost coils. Then clean coils. Once clear and airflow back to normal turn compression back on to cool. If it continues to frost and freeze up it is likely low on Freon. You will need to recharge and check unit and coils for Freon leaks.
If you have not done it already, either clean or replace your return air filter. With reduced air flow the coils are more prone to freeze up. We regularly vacuum the coils. Besides owning an IP27 with a/c l maintained air handling equipment for 36 years.