Isotemp Calorifier- repair or replace

Quandary

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Our boat is equipped with an Isotemp calorifier, shiny outer casing but rubbish design, any time the boat is subjected to a severe shock it begins to leak, the thin s. steel end cap which holds the finned heater coil displaces slightly (it is secured by one bolt through a bridge) and its edge cuts through the oval rubber gasket ring which surrounds it, it happened in 2010 and again shortly after about 4-5 years ago when we were overtaken in the Sound of Mull by a Coastguard tug going flat out leaving a vertical wave behind it about 2m. high. That time I raised a query here and finished up supplementing the replacement gasket with a generous coating of Sikaflex 291. I got four seasons out of that repair. However, earlier this month the boat was subjected to a French Canadian kiss, our boat was tied up unattended, it was raining, the guy was tightly zipped in to his cockpit when he drove his anchor and bowsprit through the floor of the suspended dinghy and pushed the pushpit into the cockpit with enough force to snap our stern rope. He was very apologetic and after I refused some Canadian dollars, quickly arranged compensation to cover the estimate for visible repairs, unfortunately it did not occur to me to check the calorifier.
It was only when I next used the boat that the Navix shore power panel kept tripping and we discovered the spray from another cut gasket, so that repair is down to me. A new rubber gasket is hard to get in UK, though Norfolk Marine list them at £37 plus carriage, (more than twice the price they are in the US). The last one was £18 which at the time I thought was extortionate. Isotemp are imported by Webasto and Marathon Leisure neither of which list any spares. There are two thermostats beside the plate which I presume control overheat and mixing, both ceramic with copper probes going down a central tube. they look sound but how likely are they to be damaged by the shorting when being sprayed with hot water?
Has anyone got a recommendation for a heat and water resistant sealant, the 291 seemed soft and easily removed when I dismantled the thing but the heat resistant sealants I can find (liquid gasket) all seem to be silicone.
Since the calorifier is now eight years old, needs repairing regularly and is made of shiny but razor edged stainless steel I am considering replacing it with a British made traditional dome ended copper Surecal, the materials to repair the Isotemp will cost about £50 while the Surecal is just a bit over £300, since the boat is for sale, I do not want to lumber a new owner with a problem in the future but am reluctant to spend more than necessary.
The problem with Isotemp is fairly common, the last time someone mentioned a consignment of duff rubber gaskets, anyone managed a permanent repair? Anyone got a Surecal, is it the answer.
 

pvb

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I put a Surecal into my last boat in 2008, and the service from Surecal was good in terms of answering my pre-purchase queries. Had no problems with it, and sold the boat last year. My calorifier location was so awkward to access that I didn't consider trying to repair the old one (a Sigmar which was 18 years old). If your calorifier is difficult to access for repairs, I'd say just go for a replacement; you'll probably get the money back on resale.
 

David2452

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The element carrier in the Isotemp (now Webasto) can be problematic and we have had the issues you describe, it is often possible to overcome it by not over tightening the central nut on the yoke that retains the carrier. I have done one this week actually. Removed it to the workshop and tightened the nut until it could be pressurised and then put a lock nut on, the gasket shoulder need accurate positioning. Another thing to look out for is the shouldered washers that centralise the ends of the element, if they are not carefully centralised leakage can occur in that area. The element and gaskets should only be £35.25 retail by the way, assuming it is the basic model.
 

Hydrozoan

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I put a Surecal into my last boat in 2008, and the service from Surecal was good in terms of answering my pre-purchase queries. Had no problems with it ... .

I installed a 22l horizontal Surecal a year or so ago and am happy to endorse pvb's point about helpful answering of queries (both pre-purchase, and during installation). It has worked fine so far and although I had wondered about stainless steel versus copper, I've been pleased with my choice - though I have no experience of other types with which to compare.
 

Quandary

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Thanks guys, couple more questions-
For David, can you direct me to someone in UK who holds and retails spares, a site listing part nos. would be useful too though they are listed on the American Isotemp spares site.
For Pvb, how durable is the outer surface of the Surecal, we carry a liferaft, flare canister, cockpit table and a couple of folding bikes in the same locker as the calorifier.
 

pvb

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For Pvb, how durable is the outer surface of the Surecal, we carry a liferaft, flare canister, cockpit table and a couple of folding bikes in the same locker as the calorifier.

As I recall, it's a fairly tough plastic outer surface. Mine was in the engine compartment, so nothing was stowed against it. I don't think it'll be a problem to have stuff stowed with it though.
 

JohnGC

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Plymouth
Had the same problem last year.

I would have replaced the Isotemp but I couldn't find an alternative to fit in the existing location. (I'd have lost quite a lot of water capacity.)

In the end I bought one of these;
http://www.ebay.co.uk/itm/2-1-4-BSP...075?pt=LH_DefaultDomain_3&hash=item1a01b5f2c3

Removed all of the fittings.

Used an angle grinder to remove the outer case and insulation at the business end - rather like taking the lid off a can.

Got a local welder to weld the new flange into a plate an then weld the plate to the Isotemp (£20 ish).

Replaced the end insulation and cover (now it's just held on with Al duct-tape).

Replaced the fittings - needed a couple of attempts to get it drip free.

Fitted an immersion heater with a standard UK 2 1/4" thread (£20 ish).

The immersion heater has a titanium element which is supposed to be suitable for use with stainless steel although I have read that people still have problems - so far so good.

I've actually fitted a high power heater and in retrospect I should have sourced a lower power unit. Having said that the electricity supply at our marina is quite capable of running it.

So far so good, but I feel it's early days.
 

Hydrozoan

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As I recall, it's a fairly tough plastic outer surface. Mine was in the engine compartment, so nothing was stowed against it. I don't think it'll be a problem to have stuff stowed with it though.

Yes, though it does dent a bit if sharp things are pushed hard against it. (BTW, another point to make is that the Surecal came with PRV and mixer valve system included, as I guess the OP has established.)
 
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