Hey...it might depend on the year of the boat, but my 1989 3818 has the AC seawater pump under the hatch in the master stateroom, near the seacock and intake, and near the sea strainer. The same intake, sea-strainer, and pump feeds both the main cabin AC and the stateroom AC, so it's possible that it's anywhere in between (or perhaps the prior owner moved it for some reason).
Worst case, turn everything else off, turn on one of the AC units, then listen for where the pump noise is coming from.
Comment