Hot Water tank not working properly

Kiwi Steve

New Member
Hi fellow boaters

I have an Atwood 6 gal hot water tank in my 2005 sail boat. Having just brought the boat can only assume the hot water tank is original.

The Issue:
Plugged to shore power no problem and the water temp heats up to or near the advertised 140 degrees
BUT When the engine (Yanmar 2GM20f) is running for up to 2 hours tank water becomes lukewarm nowhere near hot. Never gets warmer than this.

Have checked (by hand) the external temp of the in/out hoses both at engine and water tank end so know there is definitely hot hot water going in although no idea about flow levels.

Does anyone have any suggestions on what else to look for?
Appreciate any help