We are new to this so here we go... New to us this spring C40. Everything surveyed fine and worked flawlessly during the couple of weeks were able to enjoy the boat when first purchased. Now we can't seem to get things to cool down below 78 degrees. The boat was maintained during our absence (8 weeks or so) including system flushes (Barnacle Buster)
Recent history, we had the boat out of the water for a couple of weeks for bottom paint and other repairs. Had HPF message in master shortly after splash down. Tech found what must have been a very clogged line (1 of 3). The other two seemed to be at full stream. After two unsuccessful Barnacle Buster flushes, an acid flush opened up #3 so all three units were flowing enough to consistently provide 78 at night and 80 degrees-ish during the day (Sarasota area day time temps 90ish).

Within a week the master unit outflow stream looked to be about half of what appeared to be full streams out of the other two. However, it kept up with the temps as stated with no HPF. Asking around I'm consistently hearing "something isn't right, you should be able to get much lower room temps even in FL. I leave the units running 100% of the time and by generator when cruising or on anchor. I was told that is necessary in FL due to the growth issues.

Today same tech says he thinks I need to replace the AC water pump as the current one seems to be not pushing enough water through the system. He supported this with stating the unit felt very hot to the touch and the impeller looked very warn. I'm a rookie but this seems plausible, yet odd that only one of the streams is showing weakness. He thought barnacles or some other debris may have made its way into the pump to cause problems. Wouldn't a weak pump essentially provide weak flow relatively equally? His response was the extra distance the water had to travel up and back to the master made it more susceptible to low flow issues. My BS meter kicked in on that one. Hope I’m wrong.

We already have some real money in the previous “fix” earlier this month and hope to get it right once and for all. Your input is greatly appreciated.

System description:
"High Velocity" System
single 8,000 BTU unit
two 9,000 BTU units
Current pump capacity is “985 GPH at 3 ft Head”

Questions for Carver-ists:
Is 78 degrees all we should expect in this heat?
Is it really necessary to run the AC 100% of time to prevent growth from getting started? Seems silly to be running the gen when cruising and we’re up top.
Is more GPH the really the answer?
Knowing more is not necessarily better, how much addition GPH do I consider upping the game if a replacement is in order?
fyi - the "fix" earlier this month included the flushes and replacement of the strainer.