came with a custom installed watermaker
with an engine
driven HP pump
and a membrane which produces 120lph. I have only used it once, during the sea trials to ensure it worked, which it did. Now, 8 months later, I am rebuilding the complex engine cooling
system and trying to clean things up and ensure that I can maintain/repair anything that might go wrong.
Because seawater around here is only about 5-6C, and doesn't get much above 12C in some places even in summer, the previous owner, who owned a commercial watermaker
business, had the input of the watermaker fed through engine heat exchangers to pre-heat the seawater, and also to provide some feed pressure to the HP pump
using the engine water
pump. (there is a gauge for monitor
this, and a needle valve to adjust the amount of flow diverted to the water maker).
This part I understand, and am prepared to monitor
as needed. The part which concerns me is that the supply water for the membrane is seawater which has been through heat exchangers (two copper coolant/seawater units, and a Groco bronze oil
cooler) and therefore have the potential to introduce contaminants (oil, coolant) into the watermaker loop, which could affect water quality, and damage the membrane.
I have read a lengthy thread here about the reasons not to use shared through-hulls for watermakers (although mine is different in that the seawater source is at pressure after the raw water
pump), but my question is more related to the issue of potential contamination of the seawater source due to the coolant
heat exchangers. I am interested in hearing some feedback on this, and if any others have encountered systems like this, or alternatives for warming the seawater intake to the WM. The previous owner and designer
of the system stated that the membrane is more efficient if the intake water can be 20C or above, so I could forego the pre-heating of the seawater if I can accept a lower WM output rate.
As an aside, in that other thread (https://www.cruisersforum.com/forums...ke-135029.html
) flow rates for Yanmar
engines were quoted, which I found interesting, as the Jabsco raw water pump
I have is rated at 7.5GPM, yet my engine is probably equivalent to a 4cyl Yanmar
(VW 1.6L diesel
, 50hp) in terms of cooling
needs. The engine still runs strong after 20+ years and >4k hours since a rebuild
, and temperature rarely exceeds 180F. This may be due partly to the engine being oversized for the boat
, so it doesn't work
all that hard unless I am cruising near hull speed
. I just found that interesting, and would be curious if those Yanmars suggesting 16GPM flow actually use a 16GPM raw water pump
? The output from my exhaust
always seems to be a lot higher flow than most boats of a similar size.