Hello all,
I think I probably have some air trapped in my hot water heater.  I have found 
some pretty cryptic instructions for the heater, but:  

a). They do not include a good drawing or explanation of how the hoses, either 
fresh water or coolant should be connected (yes I have looked for better online 
instructions to no avail)b). They say "Bleed air from the entire coolant system 
for proper operation of both engine and water heater", but don't give 
instructions as to the best way to do it.
c). They do not include a listing of the what the stamped letters next to the 
outlets mean.  (the upper left in the photo is "H", bottom left is "D", upper 
right is "P1" and lower right is "C"

Here's a photo of the water heater:  Attwood EHM6-SM Water Heater.j
The tube in the upper left feeds the boat with hot water.  I think the tube on 
the bottom with the valve on it comes from the engine hot water feed.  I turned 
off the valve, and the hot water continued to run, so it is definitely not the 
fresh water supply line to the heater.  And, having a valve on the hot coolant 
input line would make sense.  Therefore, am I correct in thinking the pipe on 
the lower right would be the return coolant line to the engine?
Now for conundrum #2.
Here's a photo of the hoses leading out of the engine.  Hot water heater hoses 
at engine.jpg.  Those hoses connect to the grey solid pipes shown in the 
previous picture, somewhere under the floorboards where I can't see which is 
which.  They were disconnected, but filled with coolant when I got the boat, so 
I was just guessing when I connected the hoses to the engine.   In looking at 
the Yanmar manual, it appears the red hose should be the suction side coming 
from the water heater, and the black hose would be the pressure (hot) water 
coming from the engine to the water heater.  Am I correct?  

Any way about it, since the water going down to the heater must flow down under 
the floorboards, up to the heater, then out of the heater and back down under 
the floorboards, the water heater would be a prime spot for air to get trapped.
So, I am thinking I should ease off the connection coming off the lower right 
side of the heater and apply pressure to the appropriate hose coming off the 
engine, and see if I get any air out.  Then, I want to ensure I am connecting 
the correct hose to the right inlet/outlet point on the engine.  Does this make 
sense?
Thanks for your insights!

Bruce Whitmore

(847) 404-5092 (mobile)
bwhitm...@sbcglobal.net
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