Its pretty simple to determine if you have a plugged strainer. Turn the A/C system on and see if you have water exiting the discharge ports on the side of your boat. If you have a good stream, you filter is fine. If you do not have stream, check the filter and make sure the pump is running. The pump will be located close to the filter. If the pump is not runnnig, you may have a bad relay and for that, unless you are experience in electrical components and how to test them, I would suggest you seek outside help. My system is CruiseaAir and the relay cost about $80 and can be found online. Pretty simple to test and replace if you're experienced in this area.
Ultimately I have probably ready my manual cover to cover however not at one sitting as I could not retain that much information. However that is usually the first place i go when i have a problem. Some information in the manual is very helpful and some not so much. If you have reasonable level of mechanical ability, you should be able to perfrom a lot of tasks on your own using the manual and online sources.