3/8" Hose to Water Heater

[Stu Jackson]

Found this from Ward, with a C30, over on abo:

My M25-XP has two short lengths of 3/8" hose running from the thermostat housing to brass adapters where it transitions to 5/8" hose.  Time to change out these hoses.  I checked with the usual sources and the only 3/8" marine hose I can find is fuel line and silicone heater hose. The silicone heater hose is not fuel/oil compatible.  Anyone know where I can find 3/8" hose suitable for this use?


He found this:

Found a hose that will work at the local AutoZone. I had to look through their formed coolant hose rack to find it.

Dayco 87001 is a 3/8" ID Formed Coolant Hose about 14" long with a 90 Deg bend at one end. It will give me the 3/8" 90 Deg formed hose I need as well as the 3/8" straight hose.

[Noah]

Ok. Now you have both forced me to look on my engine to find out what the heck hose you are talking about. So much for ignorant bliss!

[jmcdonald]

Isn't there just engine coolant running through it? A mix of water & antifreeeze. Just like in your car. Automotive heater hose would work just fine.

[KWKloeber]

Stu,

Shields series 160 water/heater hose comes in 3/8".  p/n 116-160-0380
West Marine carries it; SKU 6556369.

Here's the description:
Shields 1600 Water/Heater Hose has a good bend radius, is fabric reinforced, and has an EPDM tube and cover.
This hose is primarily used for critical water connections, heat exchanger, toilet intake, small engine intake, bilge pump
intake/discharge, and below water line drains and scuppers. It is resistant to mild chemicals, heat, cold, ozone and
saltwater. The temperature ranges from -40°F – +190°F; 250 psi.

The downside of the Series 160 hose is that the temp range is a little lower (190F) than Shields series 200 or 250 hose (200F).

3/8" silicone heater hose is perfectly acceptable to use on water heater connections, it's made for engine coolant so long as it's SAE J20x rated.  It's a bit expensive but HPS Silicone Hoses carries it.

-k

P.S.: McMaster-Carr also carries 3/8" silicone heater hose., item # 5133K22.

[KWKloeber]

Noah,

The OEM Kubota engine has a thermostat bypass hose that runs between the lower thermostat housing (water flange) and the coolant pump.  It's critical purpose is to provide coolant flow thru the engine while the thermostat is still closed, so the block doesn't experience hot spots.

Part #8:


Catalina removes the bypass hose, and connects the water heater supply and return hoses to the hose nipples.

The alternative to the hoses I in my previous post below is to buy the expensive OEM bypass hose, Universal p/n 300236, and cut it to make short connectors.



or Kubota p/n 15531-73350:




-ken

[Noah]

A ha! Thx for the tutorial!

[KWKloeber]

I hope it wasn't TMI "engineering"   

[Paulus]

Stu, you might give Kent Rubber in Muskegon a call.  They specialize in hoses and fittings.  1-231-798-7675   I do not know if they are a nation wide outfit or just Michigan.
Paul

[Dave Spencer]

Thanks for posting Stu. Your posting reminded me that it's getting near the time when I need to replace my thermostat to water heater hose.  I've read most of what there is to read and it seems the most difficult part is feeding the hose under the floor to the heater. Here's Stu's 2007 write-up... I'm sure there are others. 
http://c34.org/bbs/index.php/topic,3769.0.html
In order to ease this process, I was thinking I would run 3/8" coolant hose under the floor to a convenient spot by the heater where I would use the adapters to transition to 5/8" to fit onto the heater.  Clearly 3/8" hose would be easier to fit through the hidden part under the floorboard and just easier all round to route. There would be some marginal increased resistance to flow but I doubt it would be significant since the coolant is already flowing through several feet of 3/8" hose.  (I'm not going to dig out my fluid dynamics textbook to do the math on that.)
Does anyone see a problem with this approach?   It seems to have the double benefit of being easier to install and less expensive which makes me wonder why it wasn't built that way in the factory. 

[Ron Hill]

Dave : Which ever hose you use 3/8" or 5/8" when finished - slide some 1/2" or 3/4" pipe insolation over the hose.  It will protect the hose from laying on the hull and possibly sitting on sharp fiberglass chards!!

A thought