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MHRitter 10-26-2002 09:30 AM

Water Heater By Pass Valve
A Catalina 38 owner sent in a picture of his by pass valve installation and
it is on the following web page:

He reports about 7.5 knots using a 16 inch, feathering Max-Prop
set for # 16 in the Max-Prop book. As of 24 Oct he was not
sure the valve was open or closed, but he never overheated.

A Catalina 36 owner posted the following well written summary on Oct 14, 02:

> Short story: With the water heater removed the engine will stay
> _exactly_ at the thermostat setting even at full throttle.
> Since I changed to a larger prop, my M25 engine became cooling
> limited. That is I had to reduce the RPMs or the engine would
> eventually (after about an hour) over heat. With the old 15x11
> fixed prop I did not have a cooling problem but with the 16x11
> folding prop I do.
> Easy fix. I opened the heater by-pass valve. I have a 160F
> thermostat installed and with the bypass valve open the engine
> will not heat about 160 even at 90% throttle for an hour.
> I was able to do a pretty conclusive test as I had to motor in
> dead calm at 8:00am to a race start.
> What this proves to me is that having a water heater plumbed in line
> with the engine coolant greatly reduces the engine''s cooling
> ability by slowing the coolant flow through the engine and the
> heat exchanger. With the bypass valve I can switch the water heater
> in and out of the loop in a second by turning a 3/4" ball valve
> handle and can see the effect quickly

cnaccarato 10-28-2002 09:36 AM

Water Heater By Pass Valve
I''m just about to put my water heater in series with my engine and thermostat. I have a Yanmar 3QM30F. Do you have a drawing on how you did yours with the by-pass. On my yanmar the distance between the eng. and thermostat is only about 4".
Chuck -SV Sirena

MHRitter 10-31-2002 10:41 AM

Water Heater By Pass Valve
Please understand that I do not advocate the bypass valve scheme required when the water heater is in series with the heat exchanger. Also pleas understand that the engine manufacturers now recommend the use of the thermostat bypass circuit for the water heater. see to look at the different options.

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