Hot water woes

[typhoontye]

Good Day,

I’ve had consistent problems making house hot water from the engine coolant. I have an Isotherm hot water heater, located above the engine level, in the port side lazarette. I’m considering installing an in line pump in the plumbing circuit that leads to the HW heater inlet. Has anyone done this? And if so, what pump did you use?

David
Blue Moon
#189

[robshookphoto]

I had problems so I took the water heater out of the loop and just ran it off the inverter while the engine was running. I don’t see any advantage to heating off the coolant.

Pearson 424 cutter - "Effie"

[typhoontye]

Thanks Rob. We’ve taken to doing the same. Not a bad work around, and am grateful we have it! But often times I also need to replace amp hours in the battery, and the inverter pretty much uses everything the alternator puts out. So I end up using the engine longer than I’d like…

David

[rdugger]

PO repowered Eclipse with a Westerbeke 63…the routing of coolant to water heater was sort of a by pass and not in the primary flow so water heater was slow to get water heated. Rather than change several hoses and their routing , I placed an in line 12v continously duty pump to move coolant to the WH with a switch at the nav station. Problem solved. Pump has work flawlessly for I think 15 years or more.
Not at the boat so I can’t identify the pump at this time

[Rich Harris]

Dunb question maybe but do you have a coolant overflow tank higher than the water heater so all the air can be burped out of the system. Forget Knot had a similar setup to yours and it worked fine for us. I now have the new water heater lower than the new engine (long story) and we have no issues.

[typhoontye]

Thanks for the replies, guys. On a sidenote, we have a W58, but not the original. Ours differs in several respects, not the least of which the extruded exhaust manifold is mounted backwards (to us). It was originally intended for a conventional install, with the front of the engine pointed forward, toward the bow. It hasn’t been an issue as the exhaust hose makes a sharp turn aft, towards the water lift muffler.

There are two ports on the extruded exhaust manifold which are intended for the heater hookup. One labeled ‘in’, the other ‘out’. Sadly, some person who owned the motor prior to me, welded both of these thoroughly. You might be thinking, why didn’t he just install bolts in these unused holes? I ask the same question, but what is done is done. So, when I installed this engine in Blue Moon, I tapped the thermostat housing for the pressure end of the water heater circuit, and plumbed the return end to just below the extruded exhaust manifold, where the engine plumbing returns to the suction side of the engine coolant pump. Sadly, this doesn’t seem to be providing enough ‘blow and suck’ to move sufficient coolant through the water heater. Hence my question about the in line pump. So, RDugger, I appreciate your input on the pump. I’m debating with myself, which type of pump to install. A centrifugal type pump seems to make sense. But it won’t self prime. Don’t know if that will be an issue. But it can spin ‘dry’ with no ill effect. A self priming pump, like our bilge pump, would probably burn up in time, particularly if it isn’t getting any fluid. Plus, it would be passing very hot water (hopefully) and antifreeze. Don’t know if it would be up to this. So if you happen to come up with any more details on your pump and it’s install, it’d be great to know!
Rich, to answer your question, yes, our overflow reservoir is located high up. At the top, aft end of the port side lazarette. I would certainly be interested in knowing more detail on the location of your water heater in your current set up.

Thanks to all who responded!

David

[rdugger]

I won’t be back to the boat for a couple of weeks to pull a model number on my pump… but I did find an email from 2009 back when we had a 424 listserv where I mentioned I used a 12v Jabsco pump and I do recall it was suitable for hot temperatures and continuous duty and it wasn’t cheap… I found the following Jabsco pump with those criteria… there may be others…

Jabsco / Flojet 59510-0012 Mag Drive Brushless DC Centrifugal 12 volt DC hot water circulation pump for RV, bus, marine or other circulating heating systems. Can be plumbed to engine cooling system to use hot engine coolant for heating while vehicle is underway. Handles fluid temperatures up to 212degF (100degC). Does NOT contain a heating element, for circulation only.

Direct replacement for Johnson CO10P5-2 and CM10P7-1 circulation pump applications. Pump head compatible with engine anti-freeze. Includes mounting bracket. 3/4″ hose barb ports. Magnetic Drive, no shaft seal to leak. Continuously rated. 20,000 hour life on brushless motor. Non-self-priming.

Specifications:

Output: 3.3 gpm (12.5 lpm) @~1.74 PSI (0.12 bar), max 3.9 feet (1.2 m) of total head.
Connections: 3/4″ (19 mm) bore hose
Dimensions: 3.8″ (97 mm) long x 3.9″ (100 mm) wide x 2.75″ (70 mm) high
Weight: 14.8 ounces (420 grams)
Max Current: 1.2 amp at 12 volt DC; 2 amp fuse

[typhoontye]

Thank you! Good info. That PN appears to be discontinued, but there may be some out there still. Plus, there appears to be some other options that popped up, including Jabsco products (Jabsco 59520-0000B…suitable with antifreeze). All are rather expensive, of course. Just before I saw your post, I ordered a cheapie pump through Amazon. Thirty bucks. Probably worth about that, too. But at least it’ll give me an opportunity to do a proof of concept. And I can purchase a longer lasting pump if this works, and wears out…which I suspect it will. Thank you again!

David

[Rich Harris]

David,
Our water heater was installed in the port laz. I took it out to clean and fix the jumbled hoses and once out it was apparent the heater was working on borrowed time. We relocated it under the qauterberth essentially right next to the engine. When we repowered with the Yanmar it had the fittings ready to go. I installed a quick system and it lays on its side. The 8 gallon unit fits like a glove.

[typhoontye]

Thanks Rich. That sounds interesting. I’ll file that away for a possible future mod. I would have to relocate my starting battery (in the aft most compartment under the quarter berth), or the AC unit, which is located just forward of the starting battery compartment.

David

[typhoontye]

I installed the 30 dollar centrifugal pump in series with the hose that exits the thermostat housing. When I run the pump after the engine has warmed to near operating temperature, the engine coolant runs through the hot water tank just fine. I believe that all I really need to do is run this pump for a relatively short period, and the normal pressure/suction from the engines normal coolant flow takes over and circulates the coolant without the aid of the ‘boost’ pump. I’ll experiment more on an upcoming trip. We’ll see if this solution will work for a week of cruising.

Note that the centrifugal pump requires liquid coolant (or whatever) to be present at the pump inlet. It is not self priming. So I mounted it a bit lower than the thermostat housing.

Interestingly, I asked Xylem, parent company to Jabsco, to supply a recommendation for a pump for this purpose. They replied that they don’t have a pump that meets my temperature requirements. Jabsco 50840-0012 specs say that this pump is good for engine coolant to 203 degrees F.

David

[rdugger]

Made it to the boat. The pump I installed is a Jabsco 12volt 59510-0012.
If you decide to look for a higher end pump, it appears that Johnson Pumps makes a continuous duty C-10 and C-30 designed to circulate coolant.
You might find other options via Depco Pumps
https://www.depcopump.com/
or call them … they’ve been a valuable source of info and pumps in the past.
Rick

[Author]

Posts