James wrote:
Yes, I would expect the rubber vaned pumps to provide enough of a seal when
not running to prevent significant backflow. I would recomend some testing
to run both engines in this arrangement. Differences in the pump outputs
could cause one or the other to not have enough coolant flow. Best course
would be to try it in a controlled situation and watch the temp gauges and
overflow tanks.

To calculate the cooling capacity involves the surface area as well as the
material, thickness, and temp differentials. A trial run would be more
practical.

"franc" wrote in message
...
I don't think I need to do anything on the raw water side since the cooler
consists of a bunch of rods outside of the boat in a cut-in of the hull,
hence raw water circulation is simply 'natural' and can't fail. Expensive
to install, so that's the reason for the question.
Each engine has its own rubber vaned pump for coolant cirulation, so if I
follow your story I would need to do absolutely nothing except Y the
exchanger and that would be quite simple cheap and fast... correct? I
suppose there wouldn't even be a problem if both engines were to run?
I just realized that I will also need to make sure that both coolant
overflow tanks are fairly close together (boat movements) and at the same
height.

I actually have another, unused, heat exchanger which is a flat
compartment welded against the (8mm steel) hull, which I would like to use
but I have no idea about its cooling capacity - if there is some kind of
formula (cooling capacity per surface unit) I'd be interested...!

Al

James wrote:
You may have to add a couple check valves to the sealed coolant side
depending on the type of pumps. A rubber vaned pump will prvent backflow
when it is not spinning. A regular metal vaned pump such as is used on a
marinized car engine will not. You don't give any specifics but I
presume you also have a way to provide the raw water flow no matter which
engine is running? Normally a pump on the engine also provides the raw
water flow to the heat exchanger. If you are also planning to Y the raw
side as well the same issues about check valves would apply. I have not
seen appropriate check valves for this application but I suspect they are
available. They would need to open with minimal forward pressure so
check valves designed for use in a pressurized water supply may not work.
On the other hand the check valves would not have to provide a perfect
seal. The additional complexity in plumbing may make it not worth while.
There is something to be said for simple.

"franc" wrote in message
...

I want to add another, smaller generator to my boat.
Existing and new sets have indirect water cooling.

I have only one heat exchanger and the expense of
adding another seems a little high.

So I was wondering if anybody tried adding a second
generator to the heat exchanger of another engine,
with two Y connectors at the exchanger?
Engines would have a shared indirect cooling system.
Does this work? Do I need to install one-way valves at
the outlets to the cooler to avoid cooling water to run
through the inactive engine, or is that not an issue?
Cooling capacity should be ok for both engines since the
exchanger was sized for a bigger engine (bigger than my
'big' generator) but I intend to run only one genset at
a time anyway.

Thx, Al


Your present heat exchanger, while it might be big enought to handle a
larger engine, it's probably not big enought to effectivly cool two
engines.