After checking Scot pump specs, our 1/2 hp pump specs require a 3" or 31/2" impeller. Ours has a 4" impeller which is Scot spec for the 3/4 hp motor. I doubt our pump came from Scot, it was put together by a tech or rebuilt with the wrong impeller in the last few years. Any way, decided to go with whatever the mfg specs and not question their recommendations. The new pump will be a CD100 1/2 hp by Aqua Air and should solve any low flow problems caused by the wrong pump setup. Cleaned and descaled the copper manifolds for the chiller input/output yesterday and was surprised at the scale buildup inside the piping. Apparently the system had been using dock water with low glycol mix for a long time. Like most with the makeup water being plumbed to the water tank this situation would be hard to avoid with low glycol or any leaks in the system. Something to consider when purchasing an older boat with a chiller system, would require extensive invasive work by a knowledgeable tech during surveys. We will have replaced every component of the system except the loop piping when finished. Not trying to to highjack this thread but thought this could be useful as to what can go awry over time without proper maintenance.