• On September 1st, Maine Sail suffered a major hemorrhagic stroke. One of the most generous members of our sailing community, he has helped thousands. Now it's our turn. Click here to learn more

Isotemp water heaters

NYSail

.
Jan 6, 2006
2,741
Beneteau 423 Mt. Sinai, NY
So I am going to replace my water heater and would like some advise.....Have a Seaward 11 gallon that has lasted 16 years and still going but not thrilled with the aluminum tank. Also, appears to be a lot of corrosion and feels moist underneath so maybe this is a good time. I like the Isotemp units (8 gallon due to space) but they have two designs; both have ss tanks but the "SPA" model has a Polypylene exterior ($542) with the "Basic" having a ss exterior ($738). Is there a real issue with a plastic exterior? It appears that all else is the same. Also they come standard with a 750 watt coil however can upgrade to $1,200 watt. My Seaward has a 1500 watt coil.
Would love to hear from experienced users..........

Thanks
Greg
 
Feb 26, 2004
21,957
Catalina 34 224 Maple Bay, BC, Canada
Greg, I don't think it has much to do with "experienced users" but general experience.

We've found (i.e., 1,800 C34 owners) that the lifespan of our OEM Seaward heaters is from 12-16 years, regardless of capacity. Most of us had Seaward units installed, 6 gallon size, but earlier ones had Raritans. Pretty much same life span.

When Seaward started making their ss enclosures, people wasted money on them. The guts are what's important, not the shell in the case of these heaters, regardless of who makes them. I always asked myself this question: "If the guts wear out before the shell, why was I spending extra $$ on the shell?" I'd almost bet the plastic would outlive the ss!

The wattage on the heater will be directly proportional to the time it takes to heat the water. Period. If you have a 1500 or 2000 watt inverter, and a substantial house bank to support it, it might be worthwhile to get the smaller wattage. If you only use the electric heater when you're on shorepower, then go for the bigger one. And I suggest getting into the habit of heating the water and turning off the element until you run out of hot water; just turn it on again.

All the best, Stu
 
  • Like
Likes: jssailem
Oct 26, 2008
5,015
Catalina 320 Barnegat, NJ
For my Starwind, I bought a 5 gallon IsoTemp with the plastic shell. If I remember correctly, it was less weight? I couldn't see any reason to get the SS shell, either and I didn't notice any problem with the output of hot water. I didn't have a water heater before, so I had nothing to compare it to. I placed my heater in a space at the back end of the aft quarter berth, which is a space I used like a garage. I figured the plastic shell would not show scratches. I saw no downside to the plastic shell. If there is a downside, it would be news to me.
 

NYSail

.
Jan 6, 2006
2,741
Beneteau 423 Mt. Sinai, NY
That is my feeling on the shell... kind of thought he plastic would be better. And yes I understand that the bigger element will heat quicker, however never thought about using it with the inverter so thanks for the idea....... lower voltage would be better in that case.

Just wanted to hear what others have thought about their unit.

Its funny, they appear identical except for the shell, however in the description the "basic" model says "
  • Specifically designed for use on yachts and boats, and built with highest quality components to ensure long service life in the marine environment
The other style does not........

I was just wondering if I was missing something between the two models that an owner of them might know.

All else being the same (guts) I'd rather have the plastic and save $200 and spend it on a new line....

Thanks
Greg
 
  • Like
Likes: jssailem

NYSail

.
Jan 6, 2006
2,741
Beneteau 423 Mt. Sinai, NY
So just spoke with the manufacturer... Same exact unit other than the external case. Just purchased the 8 gallon SPA Isotemp! Chistmas starts early!!

And thanks Stu.... I am keeping the 750 watt coil as I like the idea of trying my 3000 inverter with the hot water heater now that I have capable solar ability.

Thanks
Greg
 
  • Like
Likes: jssailem

Bob S

.
Sep 27, 2007
1,687
Beneteau 393 New Bedford, MA
Greg,
Does your boat have hydronic heat? Just curious if anyone has used a heat exchanger with hydronic heating and kept their hot water tank.
1634768713586.jpeg
 
  • Like
Likes: DeniseO30
May 19, 2020
65
Hunter 30 Quincy
When I replaced my leaking Seaward with an Isotemp I bought the plastic shell one and never gave it a second thought. 100% happy with it.
 

NYSail

.
Jan 6, 2006
2,741
Beneteau 423 Mt. Sinai, NY
Was delivered last night...... 8 gallon with plastic shell. Looks great!

Thanks all
Greg
 
  • Like
Likes: jssailem
Feb 26, 2009
591
Oday 30 Anchor Yacht Club, Bristol PA
Greg,
Does your boat have hydronic heat? Just curious if anyone has used a heat exchanger with hydronic heating and kept their hot water tank.
View attachment 199402
I was In HVAC for close to 50 years, learned a few things along the way... I would have to say great idea but, by time you purchase the heat exchanger and a water heater tank you'll probably find the cost about the same as buying a heat exchanger water heater already made for the application.
 
Last edited:
Feb 26, 2009
591
Oday 30 Anchor Yacht Club, Bristol PA
Stainless aluminum or even copper water heater tanks are nice and the perception that the more costly material is going to last longer is somewhat skewed by the amount of sediment which builds up in these little water heaters because, of the large temperature differentials.

if it's wet underneath, you can probably be pretty sure the tank is leaking. But check and double check all connections

If you have sulfur smell, you can assume it's loaded up with sediment.

Just replaced the one in my boat a few weeks ago. Probably had 5-8 lbs of sediment within. Was a struggle to lift compared to the new one that you could lift with one hand.
 

Bob S

.
Sep 27, 2007
1,687
Beneteau 393 New Bedford, MA
I was a HVAC business owner for close to 50 years I would have to say great idea but, by time you purchase the heat exchanger and a water heater tank you'll probably find the cost about the same as buying a heat exchanger water heater already made for the application.
I agree on the costs. My Seaward HW heater is functioning fine plumbed through the engine and shore power. I have been thinking of adding heat to my boat which would make May and October evenings more comfortable. Researching air and hydronic systems has been fun, and both have their advantages. To me the advantage of having hot water at anchor has driven me towards a hydronic system. I read a lot of sailors with hydronic heating using them but I still want to keep my HW heater running off the engine too.