Isotherm Magnum Refrigeration Concerns

[ZacharyWS]

So I have an Isotherm Magnum water-cooled system aboard my boat. It was purchased and installed in 2018 and seems to have worked well in the last year of constant use.

I have noticed its performance is slowly deteriorating and found the issue has some issues....

#1 the zinc is now toast and needs replacement. A PN is not listed in the manual. It seems to be a 1/4NPT pencil zinc, however the cavity to accept the zinc seems to be maybe 10-15mm deep. Any thoughts on what zinc goes here? I could cut down a 2" but that just seems like a lot more work than ordering the correct part.

#2 the seawater pump has some corrosion on it and is definitely the cause of the underperformance..... When I dug into this issue i ended up removing the glued vibration cover on the pump to find that its an off the shelf pump.

Pentair Shurflo AquaKing 2
P/N 4129-110-b02

In seeking a replacement I have found that this pump is listed on Pentair's webpage as follows:

SHURFLO AQUA KING™ II Jr 2.0
MARINE FRESH WATER PUMP – PRODUCT TECHNICAL DATA SHEET
OEM: 4129-110-A02
AFTERMARKET: 4129-110-B02

APPLICATION:
Multi-fixture Marine fresh water pump installation.
This pump may be used for general fresh water transfer

Is anyone else thinking what I am? Why is isotherm using a fresh water only pump as a seawater pump? Id have to imagine this is spec'd incorrectly and thus the source of the early failure.

[GordMay]

The Zinc Anode, installed on the Heat Exchange Condenser [on the Pump] for all Isotherm MAGNUM systems is model #IS-SBE00008AA, or [perhaps] #SBE00005AA on older models, as manufactured by Indel Marine.

➥ Zinc anode for Isotherm MAGNUM systems [IS-SBE00008AA] : Isotherm-Parts, Isotherm Marine Refrigeration and Parts