Well, the new heater arrived

This is a good post:

• My tub label indicated our Jacuzzi "CARESSA" hot tub was assembled in 1987.  It also said it has a 1.5KW 5.1K BTU heater at 115v, which should be 13 amps.
• At first, the best price I could find for the heater was $450, with absolutely no help at the manufacture's site!  They say they have good customer support, but just try to find help for a 28 year old tub!
• Then I found something that looked similar at INYO POOLS for $225.55.  I had to ask questions to figure out if this part might fit
• I was given a sketch via their chat, being told it was the same 17-1/4" long and the connections were 2" diameter (3/16" smaller than mine) with a 5.5KW rating at 240v.
• Doing the math on that, the heater should be 10.47 Ohms and draw 23 amps.  But if I put 115 volts though the 10.47 Ohm element, it should draw 11 amps, consuming 1.3KW, some 15% less.  So, it'll take a little longer to heat the tub -- so what?
• I ordered it on Saturday and it arrived the next Thursday
• Now that I have it, I find it was only 1/16" diameter smaller, so a good fit
• I needed to come up with two different sized romex connectors for the power and over-temp switch connections
• I bought new rubber connectors to go between the 2" ID (2-3/8" OD) PVC pipe of the tub and the 2-1/4" OD stainless steel of the new heater at Tractor Supply.
• To get the wires to exit out the bottom, I removed the 4 bolts holding the box on the heater and rotated it 180.  This made the wires fit better and I felt better about having the holes in the box at the bottom instead of the top.
• Went together great, and we are in hot water now!