Hot water heater on raw water cooled boat

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H33CRich

H33CRich

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Sep 26, 2011
228
Hunter 33_77-83 Cedar Creek Sailing Center, NJ
Larry Laurentius said:
Just a note that I was seriously corrected by a 91 year old German boat surveyor years ago There is no such thing as a "Hot Water Heater" Its just a Water Heater.After one hour of hearing this, I never said Hot Water Heater again...
LTL
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You are so right. No point in heating water that is already hot. My dock master (and marina owner) says the same thing. His second business is commercial water heaters. I have to be careful when talking about the subject when he is around so as not to raise his blood pressure...
 
H

H30Gary

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Oct 27, 2011
154
Hunter 1980 Hunter 30 San Diego, Mission Bay
This is a very interesting thread. Any thoughts on the various brands out there - Attwood, Seaward, Raritan, etc? The Raritans are pricey. I kinda prefer the square shape of the Attwood or Seaward.
 
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sandpiper10471

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May 31, 2007
763
Hunter 37 cutter Blind River
I installed an Isotemp on one of my boats years ago. I thought it was terrific. It heated the water very quickly from a raw water cooled engine and held the heat overnight - a feat that no other heater at the time would do. I would buy another.
 
Ed H

Ed H

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Sep 15, 2010
244
Hunter 33_77-83 Regent Point Marina, Virginia
sandpiper10471 said:
I installed an Isotemp on one of my boats years ago. I thought it was terrific. It heated the water very quickly from a raw water cooled engine and held the heat overnight - a feat that no other heater at the time would do. I would buy another.
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The Isotemps look nice... but comments in the archives indicate that my small 2GM will not heat the water enough to even generate warm water. :cry:
 
kloudie1

kloudie1

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Nov 6, 2006
10,048
Hunter 34 Mandeville Louisiana
Hot water on Raw water cooled QM

Here is a shot of the hot water plumbing (hosing?) on my buddy's 1978 H-33. It gets the 140 F water from the block to heat the water and gets the water hot in about 20 minutes. We have had problems with the nipples plugging with a white putty-like deposit (every 5-6 years) but when the water flows it works quite well. Hot water leaves the top front of the block by the lift lug. Returns to the fitting on the forward side of the exhaust manifold. The heater replaces a short jumper hose on those fittings.
 

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sailcruiser

sailcruiser

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Sep 6, 2011
435
kloudie1 said:
Here is a shot of the hot water plumbing (hosing?) on my buddy's 1978 H-33. It gets the 140 F water from the block to heat the water and gets the water hot in about 20 minutes. We have had problems with the nipples plugging with a white putty-like deposit (every 5-6 years) but when the water flows it works quite well. Hot water leaves the top front of the block by the lift lug. Returns to the fitting on the forward side of the exhaust manifold. The heater replaces a short jumper hose on those fittings.
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Could the white putty be a mineral deposit like lime scale? I get some of that in my filters annually. It may just be hard water that needs some cleaning periodically.

For us there isn't a tank it's instant on or off. The challenge is the lack of CNG in the area to refill. (not even publicly available for cars). Propane would likely be. Better choice this route but I resist the change. SC
 
kloudie1

kloudie1

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Nov 6, 2006
10,048
Hunter 34 Mandeville Louisiana
SailCruiser.. I suspect that the whitish goo is organic stuff (bayou growies) mixed with remnants of the engine zincs.. Lake Pontchartrain is brackish but it is a mile or so up the bayou to the slip .. the bayou is rainwater and very soft.
 
Stu Jackson

Stu Jackson

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Feb 26, 2004
22,985
Catalina 34 224 Maple Bay, BC, Canada
H30Gary said:
This is a very interesting thread. Any thoughts on the various brands out there - Attwood, Seaward, Raritan, etc? The Raritans are pricey. I kinda prefer the square shape of the Attwood or Seaward.
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Good question. Shape is only the half of it.

Attwood and Seaward are the least expensive, do an OK job but are not as well insulated as the Isotemps. In our 57 degree water here, the water is tepid at best in the mornings.

Raritan has comparable construction as the first two, it's price is not worth it.

Isotemp is top of the line, well worth it and includes a tempering valve to avoid scalding water. Very, very good units, and worth the increase in cost.
 
Ed H

Ed H

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Sep 15, 2010
244
Hunter 33_77-83 Regent Point Marina, Virginia
I am in the lower Chesapeake Bay- it's pretty salty here and I am concerned about clogging up a new, perfectly good water heater.(Notice I did not say hot water heater).
 
Bill Roosa

Bill Roosa

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Jun 6, 2006
6,990
currently boatless wishing Harrington Harbor North, MD
Well it does not clog up the engine does it? the engine is actually a harder thing to keep clean as it actuall has hot spots where the salt can "boil out". Just runing hotish salt water through a pipe is not going to clog it. course you still need a good strainer to keep the weeds out put you should already have that for the engine.
 
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Steve Dion

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Dec 2, 1999
15,184
Hunter Vision-36 Rio Vista, CA.
I do not know if the water is ever going to get "HOT" when you have a raw water cooled engine. I think that is why many of these older boats did not have a system that heats the water.
 
Stephen Trapani

Stephen Trapani

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Jun 3, 2004
298
'79 Hunter 33' HUN33190M79L Olympia
Hot water heater on raw water cooled boat Reply to Thread

Steve Dion said:
I do not know if the water is ever going to get "HOT" when you have a raw water cooled engine. I think that is why many of these older boats did not have a system that heats the water.
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I have a temperature gauge on my 2qm15 and the water never ever reaches 120, unless something is going wrong.
 
Ed H

Ed H

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Sep 15, 2010
244
Hunter 33_77-83 Regent Point Marina, Virginia
Stephen Trapani said:
I have a temperature gauge on my 2qm15 and the water never ever reaches 120, unless something is going wrong.
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Yet Kloudie's friend gets very hot water!
Kloudie: Does he have a 2gm ?
 
kloudie1

kloudie1

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Nov 6, 2006
10,048
Hunter 34 Mandeville Louisiana
Ed H, the engine in his 33 is a 2QM20H.. original to the boat.. Thing about the hot water here is that the raw water temp is usually above 68F.. and the ambient is only cold for short spells.. It is 79 F here right now.. but was 29F a couple of mornings last week.. The good thing about the QM engine is that there is a hose that connects the water from the block and head to the exhaust manifold; there is no cast-in passage. So all the hot water from there has to go through the water heater exchanger before going to the exhaust.. That water is much hotter than the stream leaving the thermostat where the bypass water flow has mixed into the stream which goes then to the mixing elbow. On the raw water GM models, the stream from the block and head is not available; the stream that is directed to the heater includes the cold bypass flow.. not as warm..
 
Ed H

Ed H

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Sep 15, 2010
244
Hunter 33_77-83 Regent Point Marina, Virginia
Thanks Kloudie- I think I will get the Isotemp, just use it while on shore power, and tell folks not to use any hot water until after the shower.
 
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Steve Dion

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Dec 2, 1999
15,184
Hunter Vision-36 Rio Vista, CA.
Some of the QM engines had a heat exchanger added to them after they were born. If you are in warm gulf water that may help too, but try heating 50+ deg. SF bay water.
 
kloudie1

kloudie1

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Nov 6, 2006
10,048
Hunter 34 Mandeville Louisiana
True.. some did have an exchanger.. I think Ed S. had some shots of a factory one, and another guy on the forum had a aftermarket one on his 33. This one is raw water for sure.. earlier this year we were looking for overheating and found a half of a fish in the thermostat. Removing the parts cured the overheating ..
 
Ed Schenck

Ed Schenck

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Jun 2, 2004
5,802
Hunter 37-cutter, '79 41 23' 30"N 82 33' 20"W--------Huron, OH

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