of the systems you are running together require a healthy source of raw water to
run. At the end of the season we run fresh water through all systems. We run
each system individually so we can keep up with water demand. We accomplish this
by shutting off the main sea water valve, removing the sea chest cover and
using a 3/4 inch hose to supply the fresh water. We can run all systems
individually with just one 3/4 inch hose at full flow. However, the Volvo
running at idle requires more water than the single hose can provide. Therefore
we use two hoses and by reducing one down to half flow, we can keep a
constant water level in the sea chest.
point being that the Volvo at 1250 RPMs (much more water requirement than at
idle), the A/C and water maker running together will require a large flow of raw
water. I would start by looking at anything that could restrict this flow.
From the raw water valve not opening completely when you turn the valve, a
rubber supply hose failure on the inside, a kink in the line, etc. I would also
try shutting off the main sea water chest valve, remove the raw water supply to
the LP Dessalator pump and turn on the sea water valve to see what kind of flow
you are getting to the LP pump.
Mohammad and Aty
Amel 54 #099
We have an A54 with a 230v 160 LPH Dessalator, water cooled
air conditioning, and a Volvo 110 HP engine.
1) When operating the Onan, water maker, and the Volvo above
approximately 1250 RPM the low-pressure gauge on the water maker drops from 20
psi to negative 10” hg, the high-pressure pump starves, and the water maker
2) When operating the Onan & water maker everything
operates correctly IF the air-conditioning is started first.
If the water maker is started before the air conditioner when the water
maker is started the low-pressure pump pressure drops and the water maker shuts
down due to low-output pressure on the high-pressure pump.
All tests were run with a clean sea strainer and a clean raw
water intake pipe, it was scrubbed with a round brush that reaches through the
What has been your experience? Any
thoughts? Thanks in advance.
Mark & Debbie Mueller
A54 – 68