Mine , for two 16k btu units, is an 8 year old March . Quite easy to service and clean out. Still keeps on working. They make all size units. Might be worthwhile for some of you to look into. Easy to find online and there price is not to bad.
Usually they just grow in there, they don’t really come from outside the boat. We re having a lot issues with them in SoFl especially after a haul out. They die, get loose and then get stuck in manifold. On my boat, I built an oversized manifold between the two chillers