Jeff,
Could you wrap the heater with an insulating blanket like a house unit? If
you have room, might help.
MMC
"Jeff Morris" wrote in message
...

Our boat normally comes with a 5 or 6 gallon tank; we opted for the 11.
THe month after it was "sealed in" practical Sailor did a review which
said that ours (Sealand?) was so bad at retaining heat they couldn't even
show it on the chart. However, it will take some major work to get it
out, so we're stuck with it for a while.